phil writes

In your case, how about removing the gravel - placing a barrier on
the ground, such as black polyethene and then placing gravel back on
top?

I removed some of the gravel and there's black polythene under it.
Underneath the polythene is riddled with the weeds roots which I'll
have to dig out as much as I can before laying some new polythene.

The weed have grown up through the polythene.

It would be nice to find a easier fix but I don't there is one after
some initial research.

It may take several applications, but anything containing glyphosate
should work. Apply it to the ground elder only (possibly bruise a few
leaves for greater absorption). It's a systemic, and works by disruption
the growth pattern, so it'll take at least 2 weeks before you see any
effect at all. But the important point in your situation is that it
breaks down on contact with soil, so, provided you don't splash it
around, your roses and apple tree will be fine.
--
Kay