Key wouldnt work earlier, locked car all ok, went to friends house, came out 30 mins later and nothing, light in keyfob lit up, but didnt unlock or anything, luckily had spare in my bag in car so opened it manually with the lock, alarm went off (thankfully) then silenced it with other key.

Drove 10 miles home using key that didnt unlock it, got out, and it locked with the faulty key

Any ideas guys?

In using "faulty" key to drive home, that has re-sync'd that fob- shuold be ok now!

Probably find you'd parked close to a 'phone mast, wifi hub, wireless door-bell or any one of a zillion other things that transmit on similar frequency!!

Next time you go there, park a good 100m away.........and make sure ya got your spare too!