We had a Moderns roof resotration done on our old PPOR about 6 years ago. As with any work you want done on your properties, you should always get at least 3 quotes. This is what we did. I also knew what a work colleague had paid for their recent roof rest on a similar size house to ours. Anyway, as seems to be the Modern way, a slick young fella turns up in his suit and tie and glossy book. He did get a ladder out and got up on the roof and invited my husband up to point out a few small problems here and there. So far so good! Then he calculates the price and we nearly fell off our chairs. Close to double what our friends had paid and about $1600 more than our next nearest quote. So we put it to him and cut a long story short, he made a series of phone calls (supposedly) to his supervisor whilst we negotiated the price. In the end we got $1600 off his original quote to match our other quote and so we went ahead.
From memory I believe we paid $2300 which included some repointing, some tiles replaced, 2 x galvinised chimney's & whirly bird all painted to match roof. Credit were it is due, they did a very nice job and 6 years on, the roof looks as good today as it did then (I drive past almost daily).
I've no doubt that there are other roof restorers who do just as good a job but do ask for the address of some roofs that they've done say 3 years or more ago and go and have a look. I often see dodgy restorations where the paint is peeling off (such as our next door neighbours). As for tackling the job yourself, we looked into this and decided not to DIY. Applying the paint is the easy but there is a lot more to proper preparation than just hitting the roof with a high pressure cleaner.
Flatout