I am always keeping an eye for Supra's in the classifieds for Agreed Valuation purposes and to see if any new UK cars pop up. There have only been 2 UK manuals for sale this Year, one at auction that sold for £47,250 mentioned above with lots of work done and another red one with low miles (48k miles) at £50k (unknown final sale price). Being UK Spec's biggest fan boy, I would be first on the band wagon to tell you if I genuinely believed it was worth £60, £65 or £70k , but it's just not an accurate reflection of the market right now. But I strongly advise you to do your own research and put it on for what you want for it even if the conclusion of that is £70k
Jason is right, it is definitely a sellers market right now but the audience has also changed significantly. There's nothing to really compare it to right now apart from Jason's car, but potential buyers are also not going to have anything but past adverts to compare it to and conclude that it is way more than those that have sold before, assuming you are getting carried away with yourself. Catch 22.