Have you tried thetopdoghouse.co.uk? They do obedience and agility one after the other on a sunday from 12 o clock (as well as at other times of course). Dogs are encouraged to socialise outside the training ring and you can dip in and out of either class if you need/want to.

I find this really helpful with my rescue collie as he tires very quickly and is still working up to full physical fitness.

I'm also going to look at tynetailwaggers.org.uk now tho, as they sound good!

Good luck whatever you decide to do and keep us updated with progress!