Well it appears I have got the phone working now. Used A2 uploader with the main and fs file at first. Didn't realise the custom files were mandatory. Anyway, the phone worked but was moaning about not being configured. I tried SEUS again which trashed it. So I reflashed and put on the custom files this time. This works. I think I'm back to the firmware version I had originally now! My 16GB M2 card seems to be working, which is nice. I can't be bothered with SEUS now, I don't trust it. I'll stick with the installed firmware version, unless you know how to get hold of a more up-to-date one. I installed:
W595_R3DA029_FS_ORANGE-SIGN_RED52.rar
W595_R3DA029_MAIN_ORANGE_LD_RED52.rar
W595_1213-2518_R9A_Orange_United_Kingdom.zip
Sony's version numbers are confusing. Nokia's version numbers and phone model codes are much easier to follow!