roofers rough idea?

[Northern Scum]

Hi, we have a house about 8.5mx5m with a single pitch roof that has a valley in it at one end (next door's house is at right angles to ours). We've been told that our tiles would not be allowed in a new build, as the angle is too shallow and there's insufficient overlap, and some are cracked and possibly going porous. It's about 35 years old, and we're having some problems. Out of interest, can anyone give me a rough idea of what's involved in a new roof, i.e. if a greater overlap is needed would new timbers be required to support the extra weight of the extra tiles (it's one of those truss roofs with angled beams everywhere in the loft) or would they replace with a similar weight roof made of different tiles?
Worst case scenario, new felt, tiles, the lot, for a roof that size, any ball park figures for a price(West Yorkshire area) would give us an idea of whether it's a"Jesus Christ" or a "Jesus f***ing christ"" type of number. Obviously I know nobody can be specific, without seeing the job and knowing all the details. We will be getting quotes but just wanted a bit of a clue.
Cheers

 

[datarebal]

it depends on the type of tile you have at the moment.. a picture helps

 

[Northern Scum]

Cheers, I'll try and get something useful when it's light but it's up there and I'm down here. Won't see much.

Nope, can't see my roof at all from the ground! Sorry. And there are no windows on the low side, just can't get any pictures.