This may be of interest. My sister lives in South Africa, Johannesburg. She has a bank account here in the UK with Nat West. I am a third party on her account, and have a paying in book so that I can deposit monies for her birthday, christmas, or emergency. I don't have a cheque book. When she requires funds transferring from the UK Nat West Account to her bank account in Johannesburg, I have to fill in and sign a transfer form, which includes the S.A bank details, home address, etc. The required amount is then transferred electronically to her account in Johannesburg.
You could try approaching Nat West. You might need a trusted relative who lives nearby and holds an account at that bank, to be third party on your account (if successful in opening one), who could under your instruction authorise transactions on your behalf. You mention that you are a British Citizen, passport holder, and pay UK taxes, so presumably sometime you will be eligible for a UK government retirement pension. My sister already has this pension which is paid directly into her UK Nat West account. You could mention this future need in your application, also that it would be convenient to have access to your money at any time you holidayed in the UK. This is something that my sister does too. Hope this isn't all too complicated an answer. I think it is worth pursuing, and wish you the best of luck.