I'm confused about whether they are still accepting the gold / basic "investments" (I put that in inverted commas because I'm not sure what the correct term is - the website talks about gold and silver "option" or "donation" or "investment"). They put a clear deadline last year and I don't think that they ever announced that it had been reopened.
They are still accepting applications. If you check out the website (www.tranmereroverstrust.co.uk) there is an option on the right hand side, something like "Options to pay". Click on that and you can join online. Or e-mail them to pay by cheque or bank transfer.