My suggestion would be to try the gasket and O ring kit .... I can't vouch for how effective they are, but at around £10 off eBay it's got to be worth a try.
Also when you take your existing one off it will serve to confirm wether yours has been the leak - though I'd say it's hugely likely.
Last thing is that the design changed part way through production - so there are two designs of regulators and gaskets.