How to fill exterior hole around gas pipe

Arrrgh

Hi all, looking for some advice here. Essentially there is a hole of considerable size (could fit my hand in, just about) around where the gas pipe enters my house at ground level (under the gas meter), and I am wondering how best to fill it. This hole is quite deep in that it goes through the outer leaf block and when you look in you can see right to where the gas pipe goes through the inner block (which also has a considerable gap around it). The gas pipe does seem to have the plastic "outer pipe" covering/shielding it. (hope I am making sense).

I think this hole should be blocked (at the outer leaf at least) to prevent water or rodents from entering... Any idea how best to do this?

I was considering using expanding foam and facing that off at the outside with something more durable, like cement or a cement style filler... Does this seem sensible or am I missing something here? This would be my approach if it were a water pipe or something but unsure if there are other factors I should be aware of considering it is a gas pipe. House, and gas installation, is about 20 years old.

10-10-20

You could use some expanding foam, but it may be just as well to backfill it with a stiff enough concrete mix (4:1 sand to cement) leaving about 2 cm to the level of the render, and then later on fill the remaining gap with a render mix of 6:1, brushing it off when partially set (~1hr) to finish the skin to match the existing render finish.

I wouldn't do it in one go, you'll probably get cracking. Paint after about a month.