I am not a roofer but I have never seen roof tiles painted before? Can you post a picture?

Ahh, I see the problem! It looks like the tiles were painted to make them look pretty sometime ago, not something I would do...
If it was my roof I would be inclined to remove the tiles and replace them with new ones because I think it will be quicker and cheaper than getting a trades person in to strip and repaint the tiles (time is money). I also don't think that painting them again will be a long term solution because they will start peeling again.
If you are going to DIY it then it does not really matter how long it takes so all I can suggest is to get the old scraper out and remove all the loose bits of paint, scrub off any dirt/moss/bird poo and then paint them again. As far as primers go, there are loads on the market, you may even find a specific primer in a place like B&Q but I would guess that the paint used for the roof tiles does not require a primer.

Hopefully one of the decorating gurus will be along shortly...

Yip it is a right bodge!

my thought

block the down pipe with a tennis ball or rag divert the down pipe into a bucket iff possible assuming its a terraced house block the gutter at each side off the tiles

paint on nitromors water based onto the lead and tiles concentrating more on  the lead and seeing how gravity spreads it

once fully coated and left to work in accordance to instructions see how the paint comes off and act accordingly

i suspect the tiles may be painted together by cappilery action preventing easy removal and possibly aiding water protection

so slap it on and see


oooo and remove the car or any other  painted item from the area[4m away if possible]

In case not obvious - try stripping the paint off the lead before replacing the tiles.

Well spotted JerryD, I did not notice that the 4 tiles under the flashing are way lower than the one showing on the very right. Something has come adrift somewhere...