At the risk of this seeming like a first-post-advert (it's not) - I had some luck with the guys at Spex hair. Can't post the link as I've just joined today - but search "spex topical finasteride" and you'll see what I'm talking about.
They put me in touch with a local GP who gave me a prescription and seemed fairly confident it was the same H&W formula. I can't confirm this though as I haven't actually picked up the prescription or used it yet, as I'm still (like many) on the fence about starting with finasteride at all. Would be really interested to hear someone else's experience with it to be honest.
