AlexW wrote:
Thus I would imagine would put the gas pipe at a depth which won't be
affected by the breaking activity?

I wouldn't take that for granted.

The mains water stop in the road is relatively modern as it was replaced
a 3 years back when we bought. IIRC the depth was at least a foot
(probably more like 18").
So I guess that end is OK too?

Water is probably the deepest, to prevent freezing. Electricity is often
very shallow.

Has anyone got a view as to whether I am just being paranoid about this
or advice as to approach the breaking carefully to avoid disaster?

You are not being paranoid. Chopping the gas pipe could mean the whole
street gets evacuated (and I don't know how much Transco would charge
you for repairing it); people have been killed or seriously injured
chopping into electricity mains, and chopping the water main could make
a very big mess.

You can probably turn the water off at the pavement stopcock. You may
need a thingee to turn the stopcock off with though.

All the utilities have specialised departments for underground plant and
(should) have detailed plans showing the exact(ish) location of
services. Hopefully that extends to private land. They may come out and
mark the location for free.

For Scotland,

Transco (Plant Location)
95 Kilburnie Street
Tradeston
Glasgow G5 8JD
Tel 0141 418 4093 office hours.

Moleseye (Scotland) Ltd
0800 800 333

Moleseye will notify all utilities, pipeline operators and the relevant
local authority of your proposed works. Given sufficient notice then can
supply you with drawings and enable you to comply with the New Roads And
Street Woks Act 1991 (HAUC Code of Practice for the co-ordination of
streetworks and works for road purposes and related matters) and the Health
and Safety Executive document HS(G)47 Avoiding Danger From Underground
Services.

You can also hire a CAT (cable avoidance tool) although whether it will
work through (possibly reinforced) concrete I don't know.

Owain