My first suggestion, if possible, would be to completely bypass any GP's because they are useless with Hyperhidrosis. Look on the internet for the most highly skilled vascular surgeon with experience in Hyperhidrosis and just ask your doctor for a referral. If the sweating really is unbareable, then this will save you weeks, or even months, in wasted money and time in referrals to doctors with no real knowledge of the condition.
The internet is VITAL for understanding this condition.
In myexperience, anything prescribed by GPs does not work in the long term in curing severe hyperhidrosis, although others have had success.
My suggestion would be as above: find a very experienced doctor with extensive knowledge of the condition and obtain a referral from your GP. In the mean time, explore tablets, driclor etc as you will most likely have a long time between appointments.
I hope it works out for you!
My topic further down the page "My experience and recommendations over axillary hyperhidrosis" might be of some use.