Thanks for all of the replies.
I had not appreciated that an active TRA raised the base of Class C from FL195 to FL245 and so thanks for the steer. It seems that the way in which the AIP and the NATS website describes current airspace classification and structure in the UK is rather disjointed which does not help with the understanding of those flying through it. It’s perhaps no wonder that overseas crews are bemused and confused by the whole thing when flying to/over the UK.
Cheers!