Matts_SW20
Yea previously had a genuine one going to replace it with another genuine and new gasket. Also going to test it in boiling water to ensure its working properly before I drop coolant and install it again. 

Genuine is the only way to go in my books, in saying that, as mentioned I have had a genuine toyota unit fail me with only 1000kms put on it. Don't ever disregard the part just because it is new or new / genuine.

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Thanks for the responses guys to answer questions:
- Yep I've always put the jiggle pin perfectly in line with the top marking on the thermostat housing. 
- I've always got the heater tap open as a bleed point when bleeding, not sure what you mean when the hose it too high? It's meant to be higher than the fill point at the back.
- My process for radiator hose is to have my partner fill at the back while I quickly remove hose, plug with finger, put plug back on. It can be problematic if I don't get it first go and spill too much coolant everywhere. I think I'm going to take Friday off and go get a set up like robk where I can have a hose permanently under the garnish that can be called upon for bleeding. 
- My water pump has been replaced but my mechanic purchased the product, I am unsure if it is OEM. 
 
I took the thermostat out today and tested it in a pot of boiling water, it works fine so I didn't bother replacing and put it back together. I also bought some fittings but in hindsight I should have got the full set up as mentioned above:

 
All evidence points to the thermostat now as I still can't feel hot water in the radiator but I've confirmed that it's working fine. Going to give it another crack at bleeding then calling it quits and chucking it at a mechanic. 

Yep 110% Toyota. What is concerning is my sensor for the gauge is not, I'll only replace that when I can feel coolant in the radiator though.

Okay so this is terribly embarrassing but everyone deserves a good laugh for providing solid advice throughout this 2 week process. Thanks again everyone. 
 
The car is fine, it's always been fine, it's never overheated or ever gotten hot enough to require the radiator. I've probably got all the air out on all 7 odd attempts I had. The issue was (get this) the $20 sensor I got from eBay thinking naively that as it shares the OEM part number it should be fine. The sensor was reading an overheat situation before it got to operating temp. As such this is why the radiator was always cold. Thermostat never opened for it to get that far.   
 
I worked it out by giving it one final go tonight thinking the only thing I've changed is the sensor, lets put the stock one in and see how we go. I also purchased some AN fittings to make up a spill free bleeding system:



 
Let it sit like that for 2hrs with one 2min run in between. Cleaned the garage found some MR2 stuff I didn't know I had and then took it for its first run with cap on half click. Noticed it took longer to warm up and never went into overheat situation. Did another lap of block to make sure. Came home turned it off and left it sitting with a spill free funnel in the back so it can take more coolant as it cools down and air leaves. 
 
Thank you all for your help and support. Have a laugh at my naive expense and we'll all carry on as we were. 

Been there many times - dive in to solve a problem and have the car half pulled apart when you realise it was something simple after all!! 
 
At least you have a proper bleeding set up on your radiator, will come in handy the next time.