I agree that there is a bit of a learning curve when it comes to VoIP but that should not deter you from having a go.
First google "voip for beginners" or "voip for dummies" and you will get more info than you could ever digest. There is a book "VoIP for Dummies", you can get hat second hand for a few quid, I even found a complete PDF copy online. Reading that should keep you busy over the Xmas break.
Don't be tempted to buy your equipment from the VoIP provider, much better to look around and get a decent bit of kit for less elsewhere. A lot of people use ATAs (Grandstream) which they plug into the back of their router. Personally, I prefer an AVM Fritzbox (I have a 7590 but a 7530 would do all you need). That gives you a WiFi router with built in DECT base, answerphone (you can configure several), VoIP support and various other functions. Removes the clutter having loads of separate boxes and power supplies floating around. You can pick them up second hand at reasonable cost.
There are loads of VoIP providers around, sometimes a little complicated to compare their packages. You can always find one where you can get a number for £1-£2 per month to try everything out without having to commit to 12 or even 24 month contracts. Once you are happy with your setup and the service then you may want to port in your BT landline number (this is likely to cost you a one-off fee of around £15=£20).
An additional benefit of VoIP is that you can use different providers: i.e. one for inbound (who hosts your number), another one (or more) for outbound calls. That gives you the freedom to pick the most cost effective provider which can save you £££, in particular on calls abroad.
And if you need more help, then you ask in the VoIP forum here or on ISP Review
https://www.ispreview.co.uk/talk/forums/phone-provid...