The result from my local garage after inspection, (an MOT testing station), is the front discs do have quite a lip but this is made to look much worse due to a build up of rust, as suggested by Magnet. The discs have a few thousand miles left and would sail through an MOT test at present, so not quite as urgent as I feared giving me a little time to decide on whether to stick with OEM or try and find a longer lasting alternative. Despite an extensive search I have had difficulty finding good quality alternatives, Brembo don't make a front disc for the SQ5, also I would only want to risk changing if someone on this forum has had a good experience and recommends a brand. The only straight swop I could find that comes with very good reviews are DBA competition discs at almost £900 a pair.
Maybe I should be a glass half full person and be grateful for having such long lasting pads rather than moaning about how quickly the discs have worn, just a shame to have to throw the pads away with 80% remaining!
Thanks everyone for your comments, I will keep them in mind while I decide whether to diverge from OEM or not, whilst still hoping someone comes along with a top quality tried and tested alternative front disc.
Rob