Hard to say, it would cost atleast £20k to £30k probably more as a good paint job is £3k to build this yourself if you did the spannering but got DJM to convert it and then buy the bits second hand and that is assuming you know the engine is good. I do not know how much of a following the puma has as don't know my ford scene well enough. My 205 Cossie is very similar really and I know a similar one to mine changed hands around £25k but needed some money spending even though it had a £10k plus engine.
Will be interesting to see really. I paid under 8k for my pug but it was in dire need of money and I have easily spent £25k in the last 12 months and I will do another 10 I bet before I am happy with it.