I did the job last weekend. Thanks for all the advice.
It went reasonably well although it did take me most of the weekend.
I couldn't get the lead to hug the tiles as much as I'd like but I can
improve that later.

I'm please I went with the lead flashing and not the plastic bonding.
It cost £130 in the end, which included about £30 on tools so it
worked out much cheaper than £350 too.

thanks
Thomas