As 237SJ indicates, the Foreign and Commonwealth Office provides the relevant information for each country on the website that has been linked to. (Note that, when looking at the info for any particular country, you need to click on 'Entry Requirements', rather than 'Coronavirus' to see the current rules for entering that country. Then, if you can get in, you need to look at 'Coronavirus' to see the rules that apply to everyone there).
The UK is currently regarded as a 'very high risk' country by the EU, meaning that entry into the EU (and into other Schengen area countries, such as Norway and Switzerland) for tourism purposes is barred to anyone from the UK who hasn't been fully vaccinated.
Many other countries are adopting similar approaches or even (as Morocco has already done) considering banning all flights from the UK.
Even if you can find a country that will accept a non-vaccinated person from the UK (other possibly than children, for whom there might be different rules), you'd still have to self-isolate at home for 10 days after your return unless you pay to use the 'test to release' scheme to shorten the quarantine period. Scroll down to 'What if I'm unvaccinated?', here:
https://www.bbc.co.uk/news/explainers-52544307