Hmm, 12 months EA £18 convert to 4 months £4.50 a month.
Ideally I want to do 3 years, is all very confusing.
The EA Access codes are the cheapest way of extending an existing and long GPU sub. As yours is due to expire on the 12th, the method you described with Live Gold codes is the way to go.
I’m not sure about EU codes, but I used Brazilian ones (with a VPN) when I did it last year, so I’d have thought EU codes would work similarly. There’s lots of good info in this thread, so it’s worth having a quick read through to clarify any uncertainty.