Just a quick (& hopefully final) update on this, got it into the lads in Bloomfield last Thursday & a weak battery & failing DDS relay were diagnosed. New battery & relay fitted Friday (for a lot less than main dealer quoted me for a battery previously) & car ready for pickup by 4pm. Car feels much more lively & responsive, stop/start back working as it should be and overall the car just feels like new again. Also came back to me washed & looking very fresh. Great service from Keith in the office & Alan & the lads in the garage. (Dunno what the lads in the other place were doing but clearly had no interest in getting it sorted.)

Thanks to everyone on here as always for the suggestions, advice & offers of help.