Contrary to what the other reviewer has posted, Clegg & Howard & *Pearl* do NOT swap houses.
Both Clegg & the Sibshaws (Howard & Pearl's surname) are "re-housed" from a terrace with a very narrow walled walkway at the front to two much more "cottagey" style houses, still in a terrace, but with a wide front area which provides some very useful space in future episodes.
No explanation is really given apart from that throwaway line.
Typically in real life, people would only actually be "re-housed" if they were being moved by the local council from somewhere deemed to be unfit for human habitation which the local authorities intended to demolish (usually described as a slum) to some other residence - and they would all be rented accommodation, often rented from the council. This is how many people in the UK after WW2 ended up being moved, often very much against their will, from old houses in close-knit communities to high rise blocks of flats.
Clearly this hasn't happened with Clegg & the Sibshaws, but the phrase has been used to explain the relocation, which was presumably *actually* due to the previous location becoming unavailable for filming for some reason, or maybe the production team just found the new houses & preferred the location. I think it's an excellent way to deal with the change, without having to go into a detailed backstory that probably wouldn't be all that funny or relevant in what is after all a sitcom. The move is never really referred to again, IIRC. I think it's very cleverly done.