You can get WiFi alarm systems from local companies or stay with the telephone linked ones, completely your choice. We had a traditional one in our old house linked to the house phone and it cost about £800 then £150 every 24 months to service - reduced our insurance by £5 per year...
In the next house we will update the existing alarm but I doubt we'll be paying over a grand to install with a local company. I'll probably go with CCTV and a top brand DIY alarm system connected over WiFi with a 4/5G mobile internet failsafe.