Here a couple to start with:

The Whitetop Mountaineers - Martha Spencer and Jackson Cunningham

Friday, Sept 16 Willesden Folk Union, The Masons Arms 665 Harrow Road London NW10 5NU

Moniaive Bluegrass Festival on 23 - 25th www.moniaive.org.uk

email mailout@foaotmad.org.uk and ask to be added to their weekly emails of oldtime stuff in the UK and I guess more details will crop up there as the time approaches.