I went to a swim smooth bootcamp a few years back. very useful when starting swimming and a decent chap, very helpful afterwards with answering questions etc.
Another useful and free distraction to keep a bit of motivation over the winter is winterswim
www.winterswim.co.uk/
You have to log a 400m time before mid November and then every couple of weeks there is a timed challenge to complete, starting at 100m and increasing in distance with the final challenge being back at 400m - to compare with your initial 400m time logged. Each challenge is ranked based on the improvement compared with you base 400m time.
There's all sorts of abilities and it has people joining in globally. Bit of Fun, free and an extra bit of motivation to keep getting the pool yards in.