We have a macerator in our cottage as soil pipe at rear and relocated bathroom to front,it's a bit noisy in use but fine other than that( it's not our only toilet,so not used solely) it pumps toilet shower and sink waste away.....ours is a bit bulky but believe there are ones that are neater these days.

You could use a builder, but there are companies that deal specifically with downpipes and guttering. Choose by recommendation and get some quotes before choosing. Facebook is a great place to find trades people.

I think your best bet is to get a plumber out to quote and see what they say.

@K OB The drain guys came to do a CCTV survey today. He seems to think I will be able to move the SVP along a boxed in section at the top of the ceiling tucked in against the wall, as there will be enough of a drop along the length to meet building regs. Then it can exit the wall on the side of the house and down in to a new access point. FOrtunately the drains on my property are all private to don't have to worry about neghbours etc.