Oh Muss what a palaver!!
First off, some surveys do tend to err on the side of caution. That's not to try and dismiss what yours says, but I know from other posters on MN and also my own experience that they can sometimes overplay issues and make them sound more serious than they actually are.
Lots of roofs have moss on them. They always flag this. Yes, you may want to get it dealt with but it's not a priority, so don't worry about it. The main issue with this is that the moss can clog the gutters. I must admit when you said there's a damp issue in the bedroom, my first thought was to check the guttering. Make sure it's clear and secure and that there is no water leaking from the gutters into the bedroom wall. Clearing the gutters shouldn't cost a lot - if you have a long enough ladder and don't mind heights then you can do it yourself. It's cold and messy but quite satisfying!!
If the gutters are OK, then the next thing I would check is the pointing on the wall in front of the bedroom. If this has given way then it could account for why the damp is there - in which case you need the pointing to be repaired. Again you can DIY it if you want or get someone in to do it. It shouldn't be expensive.
Asbestos in the ceilings is a specialist job - no two ways about it. You do NOT want to be messing about with that yourself. Find a reputable company, check they are fully insured and get quotes for removing it. However it is only an issue if you are planning to dislodge, remove or change something on the ceilings - so unless you're planning to refurb and pull down the Artex on day one then it can wait. Asbestos is fine as long as you leave it alone (there are a lot of older schools and public buildings which have asbestos in them).
Roots making the boundary wall unstable will need to be sorted. However this may not be as big a job as you think. A general builder should be able to sort this out for you. The main issue is to identify which roots are causing the problem and if possible, try and remove them.
Can't comment on radon results as it's not something I'm familiar with. My advice would be to speak to your solicitor about this - because they should know about it and this is what you are paying them for!
Our survey flagged up two serious issues. One we were already aware of (and we don't think it's as serious as the surveyor made out) and another which we didn't know about which was worrying. We had the other issue looked at by a professional, who couldn't stop laughing when he went round because apparently it's absolutely fine. In his words "I don't know what the surveyor was on about because there's nothing like that in this area. Nothing to worry about!". I'm not trying to dismiss surveys out of hand - or suggest that they are all over-egged; just that sometimes the reports can make issues sound desperately serious whereas they may not be. Also surveys do sometimes get things wrong (as evidenced by our non-issue!).
We're using ours as a useful list of things that need maintenance and attention, as you would expect on any property that's not brand new. If you are really worried about how much things like asbestos removal will cost, then you could ask for trades to go and quote now before you exchange contracts. If it's a significant amount of money then you may want to ask the vendor to renegotiate on price to reflect the work that needs doing. A word of warning though; the vendor may refuse on the basis that it's not uncommon for a 1930s semi to need work and for them to include asbestos in their construction.