Great guide, I've been through this process a few times before. You've provided a clear and detailed set of steps.
I really like the circle app, think it's backed by Goldman Sachs. There are a few places to get out of bitcoin in the UK.
I use this site to see where the best prices are.
Circle seems to be the best one so far
I believe the 'Bitcoin Spread' Circle charge is around 1.5% once the money is landed in your Bank Account. That's really competitive. Trustworthy, Reliable, Cheap. It's a good app as long as your not trying to cash in large sums of money....