Depending on what sort of work requires doing, you may need to have scaffolding erected, this should be included in the roofers price, just make sure that it is. I have had quotes from Duddy's in the past and always found them expensive. Luckily I had an extension built and the local builder that I used did everything himself and I would recommend him for larger jobs than just having a couple of slates replaced. I will not put his name on here as he does not advertise for work, he gets enough work from recommendations.