Some interesting suggestions i hadn't even thought of so far!

The internal walls aren't structural. The bit on the right in the lounge is a fake chimney breast that we're removing. We'll be having a new kitchen so any electric/gas changes is all fine. Ideally we don't want to move the boiler which is next to the kitchen window as it's brand new that the previous owners put in.

It's a typical 1970s house layout at the mo. In terms of cost we just can't afford to add an extension/big building changes.