Gable end roof replacement

Corum_uk

Three bed semi with gable ends and concrete tiles, build late 60's, in Plymouth. Tatty felt and leaks. Job would entail:
Scaffolding front and back
Strip off the existing roof
New felt and batten
Replace original tiles
Ridge and ends
No formal quote yet, but the builder indicated a ball park figure would be about £4k to do both houses, or £3k to do just one, and would take around 4 days.
Any thoughts? Should we be looking for quotes from a roofing contractor or is a general builder going to be able to do as good a job?
Thanks.

Corum_uk

Just had a written quote from one of companies listed on the Three Best Rated website.
9.5k to do both semi's
5.5k to do one
Seems very high.