Many thanks. You are right. I'll let you know how it goes ... it's probably for the best as now I'll have to sell whats in the garage to pay for the electrian (so there'll be no need a shed after all :>)
Thanks for the quick replies (much appreciated). I've just done what you both kindly advised but nothing has changed. I unscrewed the front cover off the Conatctum RCD in the garage to see if there was any charring of the cables - but they looked fine. I don't know how to remove the MCBs to see...
I've learnt a lot from this site but never posted a question before (so forgive me - and I stil ahve much more to learn, as you'll now hear). An electrician installed power to my garage and ran an armoured cable from a Wiley consumer unit in my house to a Contactum RCD...