Just a thorough recommendation for S Duddy. They just finished cleaning moss off and treating our roof, and replacing some guttering and downpipe. I wasted lots of time going through ads in the Marple magazine thing, only to have to chase people to even ring me back. One guy even kept me waiting a few weeks and then admitted he didn't fancy the job.
In the end, I was passing S Duddy one morning and popped in. They were brilliant; professional estimate service, clear written quote, follow-up call, nice lads on the job (even knocked on and asked if it was okay to drill for the scaffolding, as they knew we had a baby!!!!). Cleaned up a treat, were polite and respectful to my wife, and recommended a small amount of extra work that needed doing while they were up there, charged at a very nominal fee (after getting approval from myself). What's more, they were much cheaper than the sole traders' quotes, I suspect because they have their own scaffolding, so don't need to charge you for hiring that. Can't recommend them enough - please support this great local business if you have any roofing jobs that need doing - and don't assume just because they are a more sizeable business they will be more expensive.
PS - If anyone recommends water jetting your roof to get the moss off, and then painting it, run a mile. The first person I contacted recommended this but everyone else I contacted said 'no way' and their view was no respectable time-served builder would do this.