Thought I would ask if there is anything I can do to sweeten up a Birmingham Webley Hawk MK3?

I was given this rifle recently in bit of a sorry state, it's now all stripped down, cleaned and degreased, bit of rust on action/barrel cleaned up okay with oil and wire wool and stock will be refurbed.

Looking around an O-ring seems the common way to improve the piston along with a deburr and polish in the right places, but what else can I do?

Any ideas greatly appreciated..