Are these giant weeds or something else?

Any plum trees nearby? Or damsons?

They are growing vertically rather than horizontally if you see what I mean, about a metre high.

Bluntness I see where you're coming from, but no. Even the ivies with the simplest leaves show some sign of the lobing, in the veining if nothing else.

Isn't that a form of ivy.?

Look too tough a texture for birch, and birch doesn't usually sucker. Is there anything else close by? Are you certain of your birch id? Does look like tree suckers.

That could make sense actually as they are quite ‘woody’.

There is a large birch about 6ft away. Could it be that? We also had some problems with roots going into a drain.

Looks like 'offshoots' of a tree, is there a big tree nearby with similar leaves?