United Pharmacies are the online pharmacy.
Obagi Nu-Derm uses 0.1% tretinoin (pea sized amount) mixed in the hand at time of application with similar amount of hydroquinone cream. It was found that this combination actually switches on the DNA which produces collagen. (This is what they told me on the Obagi course anyway...).
Obviously these are prescription drugs for reason, ideally you need to pay an aesthetic practitioner whose been on the obagi course hundreds of pounds to get your hands on the drugs.
If you look up Obagi Nu-Derm the before and after photos are great but there is a lot of downtime initial few weeks are awful, red flaking skin etc. you can find Forums where they discuss how bad it is!
You must use complete sun block 50 with these drugs. Can use lower strength tretinoin if you wish. Ideally no oil in other creams / cleansers as tretinoin doesn't like. No if pregnant.
I can never go the distance your supposed to use for 12 weeks! I use it once a week, every now and then. Skin does bloom eventually but the peeling and redness are horrific. This is were if you've paid hundreds of pounds to somebody in this country they can hold your hand, tell you this is normal, remind you to put on sunblock and if the red/peeling is too much advise you to put hydrocortisone cream on, but this is only delaying the inevitable as all that skin has to come off to get at the good stuff underneath.
Although I'm feeling cynical today the best advice is "only to be used under medical supervision".