I can't remember what I used last time to cut a worktop. Pretty sure at
the advice of the local DIY gaff I used a jigsaw and guide and it went well.

I have a circular saw too, is there a suitable blade for that?

I do have a router but one of the knobs is broken making using it a bit
of a faff and a wrestle (and I don't know where/what condition it is
in). But if that's the most sensible option i'll find and fettle it.

The edges will be up against a wall and a tall unit so don't need to be
mint.