you also have my sympathies.
i bought indorex house spray from vets.co.uk ( IIRC ), as they were cheapest. i bought 4 cans and used the lot on my ( not large ) 4 bed house. sprayed the inside of the vacuum ( henry ) used with bags, to kill any eggs that were hoovered up, and bined the bags after.
washed floor-length curtains and my bed coverings, sprayed matresses – basically any cloth that extends within a foot of floor level.
washed all the dog’s bedding that could be washed at 60degrees, binned anything that couldn’t be washed ( or that didn’t survive ), dried outside in sunlight ( as eggs can’t survive exposure to UV ).
hoovered one room at a time and sprayed, moved every piece of furniture and hoovered beneath and sprayed around/on, which wasn’t so easy at the time, by myself, with a broken collarbone!
also got ‘prac-tic’ treatment from the vet, which is what they recommended, and had left over frontline from when the ex-GF was in charge of this stuff ( she seemed to have accepted we had fleas and that nothing could be done 😕 ). i alternated the frontline and prac-tic on a shorter than recommended time-scale.
seem to have shifted the beggars though, as i haven’t seen anything on her for ~ 2months, even though the weather here in the sw has remained good and warm. i was brushing my mutt twice every day, and pulling between 1 and four fleas off her each time. now i brush her once a week, when i remember, and she’s clear every time.
keep at it. it’s a big relief when you realise it’s sorted.