BT, Matchbox used to do a very nice RN/RAF Phantom in 1/72nd scale. Hasegawa have recently re-released their RAF Phantom, and I THINK the RN one, in 1/48th scale. Both are the same kit really, as the minor parts for the FGR2 and FG1 are included. I have the original 1980's RN version, which I did as a 43 Sqn RAF machine. If you can only get the RAF kit, and want to do the RN one, I've still got the decals, and the colour scheme sheet etc.
BTW, the kit price is the same as it was around 1986, about £26, and I believe both Hannant's and Model Hobbies have stock. I'm not sure, but I think I saw a Revell 1/72nd scale kit also, which will almost certainly be a re-issue of the Matchbox kit.