Family carol concerts and church services in London - recommendations?

[cleanandclothed]

This will be our first London Christmas with DS (3). I would love to take him to some carol concerts and advent/christmas church services - any suggestions? Central or South East London (Southwark) suits us best. Preferably something not mega-expensive or that involves queuing for ages. We will probably go to our local church for their 9 lessons and carols, and was wondering about the Christmas Crib service on Christmas Eve in Southwark cathedral. Does it get very busy? Any other suggestions?

There was something on here earlier about Westminster Abbey and the person who had gone said they walked straight in.

Christingle services are always child-friendly, you can search for one by postcode here:
www.childrenssociety.org.uk/in-your-area