Thanks Lloydie and Al for your replies
Mine don't line up atm, but seeing as I had to replace both wheels a few years ago due to corrosion (you've probably forgotten that), I was wondering if I made a mistake by not fitting both disc's inline when I swapped them over. I realise it's not dangerous to fit them either way.
I have a feeling I read somewhere that some manufactures did fit disc's so they didn't line up to help combat pulsing when the brakes were applied, of course I could have got that bit wrong
Chris.