I bet for a fiver most resorts you travel to will have british brands of shampoo!!!
I'll take you up on that bet as far as Cuba is concerned which is where Dramaqueen is going to - could be the easiest fiver I've ever made! I've never seen anything I remotely recognise in the way of toiletry brands out there - even in the hard currency shops or pharmacies or in the tourist shops in the hotels. And what is available is usually of poor quality and relatively expensive for what it is. I always leave whatever I have left for my hosts and they are always really grateful. In addition to making sure you take your own favourite brands (and stocking up at the airside Boots is a really good idea if your check-in allowance in on the low side) do also take your own tampons/sanitary towels with you if there's even the remotest chance you'll need them. Tampons are non-existent in my experience and friends found the local towels to be very inferior to what is available here.
To be honest, it's best to take anything you can't live without with you to Cuba. The only things that are of equivalent or higher quality and cheaper then here are the cigars and rum
Even though they grow coffee, the quality of what is available locally is usually awful - all the best stuff goes to the export market! Nobody goes to Cuba for the shopping!