It is very difficult to change your domicile from the UK to another country for fairly obvious reasons - if it were easy then every one would be doing it as they approached the "great day for the final departure"
As has been said above, you need to move all your assets off shore and at the very least ensure you do not directly own any property in the UK (although some people have moved assets into trusts). Your pension being paid from the UK is OK and will not make any difference to the outcome. My suggestion would be that you ensure you spend as little time as possible (certainly well under 2 months a year) in the UK over the next 5-years, then get a lawyer/solicitor to write to the relevant authorities in the UK informing them that you have severed all links with the UK having lived and been taxed in Cyprus for the last 5 years. If the UK authorities do not accept this then try again every 2-years.
At the end of the day you might have to renounce British citizenship and get a Cyprus passport. It is not easy, as this would create a huge tax loophole for the avoidance of inheritance tax.