Hello, I Would Greatly Appreciate Your Help Please... I'm Currently

Hello,
I would greatly appreciate your help please...
I'm currently being prescribed clexane injections 120mg to take on a daily basis until at least September 2016...due to suffering from 2 incidents of dvt/pe concurrently. After such time, I may be transferred to warfarin depending on haemotologist reports. I've decided to go travelling to Thailand for 4 months on March 6th 2016 but my gp has just told me that she's not happy to prescribe me the amount of clexane that I need to cover the trip. She is suggesting that I find out if I can buy it in Thailand myself as it isn't a prescription drug anyway! I know that here in the UK a box of 10 injections cost £100 and I'd need 12 boxes at a cost £1200! Surely she shouldn't have a problem with prescribing me? I'm now extremely worried and need some advice...please help
Many thanks
Tina