Remove Tiles/Felt for access to plumbing? DIY?

We have a dorma bungalow which is about to have a new boiler, the plumber needs access to this roof void to put 22mm heating pipes in the corner, if access cannot be achieve easily either the ceiling will need to come out a little, or the piping along the ceiling.

Can the roof tiles be removed from the bottom up, and the felt rolled back easily? Is this a DIY job?

The plumber commented they could remove a tile or two, cut the felt underneath and put it back. I am unsure if this is acceptable?

Could the plumber leave it, and let me re-felt the area?

Access from the inside does not look too good, it may leave the size of a small child access.

In principle, yes. You might find that the bottom edge of the felt has been fixed with a mortar fillet, which you could remove and replace. If you're doing any patching of the felt afterwards, make sure your overlaps run downwards, so any water running over the higher piece will continue over the lower piece rather than under it.

Cheers
Richard

make the access hole behind the rad