Get rid of the bash ring, or at least get rid of the excess so you only have the bottom part left. Try some of those plastic bmx pedals and maybe some foam grips (i know you said you didn't want to spend much but that'll be 25 quid or so). Drill out your stem clamp, drill your bars. Shave your cranks. Get rid of the bashplate mounts. Erm, thats about all I can think, I'd be dubious about drilling any of the frame myself. Hope that helps.