I’m using an ubiquiti wireless access point off mine and its better but it does still occasionally timeout then instantly reconnect… I’m going to blame the router too.. seems identical to the BT one but slightly worse in operation!
I’d recommend a TPLink – havent looked recently but they have always done me well.
I’ve got a Netgear one in the loft unopened going spare if you don’t mind going second hand? I’ll dig out the model when I get home if you’re interested, but it’s been grand for us. Gigabit ethernet and dual band WiFi are the bits I can remember.
Connect a laptop / PC via a network cable and see how it behaves, if all is well and it is just the WiFi then the suggestion above is perfect. Purchase a Ubiquiti wireless access point. Otherwise if you want a VDSL router with WiFi I don’t think you will get any better than what you have for £50.