On 17 June, 11:23, JohnF wrote:

Many thanks for any advice whatsoever.

Easy, but takes _ages_

Hydrochloric ("brick") acid cleans them.

Bitumen is very hard to clean off completely. Heat "gets it flat", but
nothing seems to make them "clean" on the visible surface.

New tiles are dead easy to find, so long as you want terracotta or
black. Pale ones generally need to be recycled from salvage yards, but
there are plenty around. Brand new encaustics (two shot coloured
moulding) warrant a trip to the tile museum at Jacksfield up the
Severn Valley (be warned - that place can get expensive!)

Buy a powered wet-disk tile cutter. Plasplugs is OK, chromed steel top
model is bad, Aldi's big one with the big overhead disk is best of all
(cheapies). Angle grinder gets used in corners, but really you're best
doing it wet.

Sub-base is crucial. Read the paving expert site

Peg your straight lines out at dusk, using a cheap laser.