How's about going to a monastery?
Amaravati Buddhist MonasteryThis is a Thai Forest community in Hertfordshire, I've never been, but it looks worth a visit.
Tisarana ViharaI don't know where you're based, but this is a small Burmese sangha near me in Twickenham, they do short retreats. Again, I've never been there. Check the links on this website as there are also Burmese communities in North and East London, but I've no idea what the retreat situation is like.
I hope that is some help..I wish I could go too!