Sadly, not unusual, although as Migv6 says, not entirely unique to Openreach (BT/EE, a separate company, never send anyone to residential properties, like all service providers exclusively using Openreach for the connection, they send an Openreach technician (who might then subbie it).
Albs - if you came from Sky via Openreach to BT (or more likely EE), it should all be the same same cabling/fibres, assuming you didn't go from ADSL/FTTC to FTTP. So hard to see how it could be a change of provider. It could be, if FTTC (can't be ADSL, as I'm fairly sure there is a stop sell on that now), a re-learning which takes up to 10 days, but any outages caused by that should reconnect within a minute or so. If its only on WiFi where you see the problem, it could be the (not so smart) Smarthub making a mess of channel selection. Best to try a wired device and compare, if possible, to prove it to WiFi or not.