Let's start out that I am in the USA so may not have a full answer for someone in the UK. That said fishing line that is identified as "fusion" works well for smaller control line models and there even was a push this last rules cycle for using them in CL combat here in the states(it did not pass). Remember that any knot reduces the breaking strength at the point of the knot by as much as 50%. Look up knots for fishing on the web for best results. Here in the states there are craft stores that sell beading supplies including .008 and .012 stainless wire in suitable lengths.
Bob Furr

If you go to the Brodak website the international dealers are listed and it is likely that you will be able to source steel lines pretty easily.