Try Norris's at Beaulieu tomorrow Beth (the main one on the left going down the hill into Beaulieu from Hythe, where they sell all the animal feed). I expect they'll be open and they sell Hibiscrub much cheaper than chemists. I got 500ml for £4.85 there a few months ago. They do an even bigger size but I thought that might go out of date before it got used up.
If you're still stuck, PM me and I'll get some of mine over to you.