This sounds a bit farfetched to me. I'm 40+ and lived in the UK all my life. Growing up we only had 1 phone socket in the house for the first few years until my dad got an extension put in upstairs. I've lived in multiple cities since then and no flat or house I've lived in has had more than 1 phone socket including the house I eventually bought and live in now (which is not small by most UK standards).