£100 here plus £20 for new one-shot hub nuts with the local mobile service chap. That was a full chassis check inc including brake pad check (hence the one-shot nuts) and brake adjustment etc plus gas and electricity check. It would have included a water check but we'd already flushed it all through so said not to bother with that.
It was fortunate we had it serviced as the guy found and fixed a gas leak where the flexi pipe in the front locker met the copper pipe under the unit.
He also spent the best part of an extra hour helping me troubleshooting a problem with the road lights at no extra cost.
I'm planning on just checking and greasing everything myself this year then have it serviced professionally again next year.
checking running gear,water,tyres etc is easy job and can be done by yourself but could raise issues with your insurance company if you are involved in an accident.(this could be a get out clause for them and we no how they like to take our money but not give it back)
Please make sure if you service your own that gas has to be done by the right people with the right equipment and shouldn't cost you more than £60 TOPS.