Try and find a cheaper supplier in Bulgaria. There are mail order pharmacies.
Try and find a cheaper drug, maybe a generic, which does the same thing.
If that fails there are plenty of online consultation services in the UK. But getting private prescriptions dispensed in the UK is usually massively expensive. That's why I've only used such a service a couple of times.
This doctor does both. He doesn't charge much for the prescription and the dispensing fee is only a few pounds but he doesn't generally do chronic conditions or conditions that need monitoring. Worth a try if you just want to safeguard yourself against running out of something.
Good luck anyway.