Or you could look at one of the many other mobile providers, Vodafone, EE, or O2. You can get unlimited 5G EE SIM for only £27 per month, falls back to 4G if no coverage, you also can get a decent price unlimited SIM from Vodafone (4G or 5G) and either only a 30 day contract or a 12 months if you prefer a bit longer and cheaper per month. The best thing to do is either buy some cheap PAYG SIMS with 1GB or more of data, and test them around your house to see who/what gives you the best coverage/speed.
There is no 5G in my area from EE,Three etc. I'll wait until Thursday and see if I get BB installed by Virgin.