As a fanatic Portuguese Spectrum user, I too had to overcome the difficulties of using UK computers here. This is how I solved it:
For the 48K model I had the composite mod made and I power it with a Radio Shack 9v adapter. The original TV out is now an RCA video out.
For the 128K and 128K +2 models I use the same adapter and have an RGB-to-RCA cable.
For all the other models (+2A, +2B, +3) I use an external hd adapter but the original connector was replaced by the one the Spectrum uses (a din-style plug). This provides me all the voltages I need except the -12V which is only useful for the Amstrad Spectrum's RS232 port. The RGB output on these models isn't the same because it's missing a chip, thus rendering my RGB-to-RCA cable useless. There is a way to fix it, but it requires an internal mod.
With the power and video output problems solved, I still had to find a way to display the PAL video. Instead of buying expensive converters, multi-systems TVs or dozens of cables, I bought a capture card with european-style TV input (less than $20 including shipping), installed the bt878 drivers from Sourceforge (free) and installed Dscaler to display the captured video in real time (free). I'm happy with my setup, but I couldn't do it without help.
