Two roofing quotes

badatDIY

First quote

Had someone to clean gutters recently, company also do roofing work. The guy noticed that 4 tiles at the front edge of my house have dropped slightly (i.e. ends of them aren't visible from the ground, they are dipping down into the gutter at a slight angle) - this was also noted on my survey when we bought last year but as there was no sign of leakage and other houses on the estate all seem to have the same problem the surveyor marked it as not too important, get it checked out at some point. I asked the guy what he thought the problem was and he suggested a rotten batten (original roof I think - about 50 years old) which he said could fairly easily be replaced to rectify the dropped tiles.

Two questions:
1) The quote came back at £270 (+VAT) to lift the 4 tiles, replace the batten and membrane, put the old tiles back on. This is in London. Is that reasonable?
2) Don't battens run the whole width of the roof? If that's the case, is it even possible to replace a 4 tile stretch without doing anything to the rest of the batten? I'm assuming regardless of the lack of leak it's a good idea to get this sorted, fix your roof while the sun is shining and all that.

Second quote

I also asked the guy if he could quote to install some sort of roof ventilation as last year we had a little issue with condensation (I think I mostly rectified this by making sure insulation was pulled away from the eaves, making the loft hatch more airtight and 'installing' felt lap vents in the loft). He has come back and suggested installing two 'brown stone wall tile vents' at the front lower portion of the roof, and two of the same kind of vents at the back in the middle of the roof. Is this likely to have much more of a significant impact than the lap vents I installed? Four vents doesn't seem many! Although to be fair our house is pretty small.

Two questions again:
1) The quoted cost for this is £400 (+VAT) - is that reasonable?
2) Is there much point getting these 4 tiles or shall I just leave it as is - as I said I think I solved the problem last year.

I know best practice is to get 3 quotes, which I may still do for each but getting a roofer around here is an absolute nightmare and the last guy we had in either smashed and hid a pint glass of mine or nicked it!