We had something similar after moving into our flat. A wardrobe caught the frame on the way through and left the door sitting slightly crooked, so it wouldn’t latch properly. I’d avoid buying a door separately and then hunting for an installer, as measuring and fitting can get messy. I’d have a look at the options from doors Uxbridge  and ask for a supply-and-install quote. We ended up saving money by getting the frame checked before ordering anything.