Durable Carry - Opinions Needed

Usually, if you're supporting early in the game (wards/courier/stack and pulling) you will likely be too poor/underleveled to make a difference in the game regardless of who you're playing as. It's just that supports generally have skill sets that don't rely on gold or levels to be effective.

If you're not the only support, and just buying occasional wards, you can do it on pretty much any non-hard carry - you'll just have a bit less good than had you not bought wards.

I would say that the closest hero to your description is Warlock - he doesn't *need* a lot of items, but his ult can still make a difference late game (and if you happen to have enough gold for agh's he can take over teamfights at any stage in the game). He's not exactly durable, though - usually when I play him, I have time to cast bonds + ult, and then die shortly after (but it's ok, since you have a golem that can kill things way better than your hero could have)

As far as I know, and I know something about dota 2, there isn't any hero that can turn from support into carry, you can't even get enough money to have both support and carry items, but there are heroes that can do some mess in teamfights and "carry" their team to victory.
One of them is Witch Doctor, I like to play him on solo hard lane for fast lvl 6 and then I start stealing kills with ulti for fast Aghanim's Scepter and ownage. Ofc I do this only when playing with my "team" :D
One another is Lich with his ultimate, which synergizes very well with most stunning ultimates (also with Chronosphere) and allows you to get some kills.

And as I said in my previous post, if you don't like to rely on team mate and want to try something more challenging, then play on mid or solo hard lane. With fast exp gain you can have huge impact on game, especially if you're playing on low level pubs where ppl tend to pick 4 carries and then lose because of no early-mid game power.

EDIT. What I also wanted to say, is that playing as hard carry is most fun when you're playing with someone you know, then you're both going on same lane (carry + babysitter) and you should have easier farm.
If you don't want to rely so much on team mate, then play with ganker. Most of them are also semi-carries, and if you're doing your job well, then you can become carry. Ofc you will never be as good at carrying as hard carry, but ganking means denying enemies farm, and you know that farmless carries are useless. What does it mean to be a good ganker? 36/2/4 in 29 minutes, enemy had 3 farmless carries, no chances.

Ah I think I might give Mid lane a go. I would initially look towards Puck for mid lane awesomeness due to seeing so many lately, or is that just Dendi fanboys taking over lol?

Based on the criteria you've mentioned, you might like Necrolyte. He's listed as a support, durable, and carry hero. Early game his aura is great harass against enemies who are trying to farm the lanes, and his heal is great sustain for you and any allies in your lane.

I don't play Puck, so I can't really say anything about him.

I can recommend you some semi carries/gankers and one hard carry that can be played on mid, you might want to look at them:
Clinkz is one of my first mid laners, he have very high damage and attack speed, also invis escape mechanism.
Nyx Assassin is annoying piece of ganker, played competetively, he can take nearly all targets in 1-2 seconds, provided he have good items.
Outworld Devourer is actually a mid hard carry that you might be looking for, he have very high damage output and his Q is doing pure damage.
Shadow Fiend - I don't know if this hero can be counted as hard carry, but for sure he is semi carry capable of taking out 3/4 of enemies hp with just one spell (I mean ulti), he also have very high damage bonus from passive and 3 strong nukes that need some practice.

If you have any questions you can also ask me on PM or steam, so we won't keep spamming here.

I've had a lot of fun with Puck lately - very good ganking and mobility, but he falls off a bit late game. Make sure you get early bottle and as many runes as possible, ganking at every opportunity, and you'll be nearly impossible to kill once you get blink (lvl4 phase shift -> blink out). Anyone with a silence ( Silencer, Bloodseeker especially) is pretty much a hard counter for Puck, so don't pick him against those heroes.

I also second Necrolyte as a (semi-)support who scales fairly well into lategame.

So for looking at mid heroes what category do they fall under for categorising in the 'Learn' section?

I think I might just find ones which I think look cool and give them a go :D

If you want a durable carry, look no further than Spectre.She deals damage based on her tankyness, so welcome to the balls deep club,where if fed,you can 1v5.

I think a character you might be looking for here is a Centaur focusing on leveling double edge, starting with the components for tranqs in to HoD.

Laning with a darkseer who starts with headdress for your support.

He provides you with life, but a reliable method of intiating with double edge, which I think turns him in to a carry

I listed you some mid heroes that look cool and are pretty strong, here some more:
Bane, Batrider, Clockwerk (my love), Death Prophet, Huskar, Invoker, Lina, Lion, Magnus, Necrolyte, Night Stalker, Pudge, Queen of Pain, Silencer, Skywrath Mage, Slark, Storm Spirit, Templar Assassin, Tinker, Viper, Warlock, Zeus.

And as I said above, I would recommend Clinkz, Outworld Devourer and Shadow Fiend if you want to play carry mid. Huskar is also nice, but I play him on hard lane against enemy carry to deny his farm.
All heroes listed here can gank pretty effectively, so you can find something for you.