I came across a guy on e-bay selling ready built GTP-USB programmers. He also offers bare boards and complete kits for £21

http://www.ct-tuning.co.uk

I've purchased a bare PCB as I had 99% of the descrete components (just waiting for the order from RS to arrive with the crystals in) - I received the board and USB socket for £5.00. The quality of the PCB is very good.

I also have the original HEX firmware and winpic800 ver 3.55g when the originator made the files available. Later versions are only supported by the commercial GTP-USB plus programmer.

I'll let you know how it performs