I'm not sure. But I've recently returned to work and had to state my GCSEs and provide the certificates as evidence, in all the interviews I had. They are relevant all the time. But I still have to do sodding maths and english tests before they'll accept me onto an apprenticeship. I could walk the apprenticeship with my eyes closed but I've been out of work so long I need something and have to start again at the bottom. But even for this position I needed my GCSEs first.
There are maths and english courses you can take. I did some IT courses with Learn Direct and they had people there doing their maths and english who never got their GCSEs.