Actually there are 3 Yak 11s at North Weald, each as gorgeous as the other - £100 would only buy you enough fuel to start, warm up and fly one circuit. Each is in private ownership - rides are by invitation only so you need to get yourself introduced - a few more fly-ins to North Weald perhaps?
There are no Yak 11s at Halfpenny Green.
Seeing a couple of the 11's formation flying is a real treat...