I agree with Grant and Barry, you don't want to be sealing in moisture, and also it will have absolutely no insulation properties. Pointing is defo the way to go if it's looking a bit ropey. You can buy extra thick grinding discs for small angle grinders that are good for raking out.
Roof repair costs will depend greatly on whether it's tiles or slates - tiles are about a quid each and quite easy to change, slates cost double that and are much more tricky. If they're clay Rosemary tiles I advise moving house :D Only kidding, but they can turn into a much bigger job.
Your mans prices seem very reasonable, so worth hanging on to him - we're a rare breed! :D

