Let's preface this by stating We Are Not Lawyers, and if you have any doubts about your right to take pictures, then you're probably better off not submitting it to us. However, there is a useful guide available which outlines your rights in the UK fairly concisely.
http://www.sirimo.co.uk/ukpr.php
Possibly useful reference: https://www.amateurphotographer.co.uk/latest/photo-news/uk-photographers-rights-print-them-out-and-keep-them-handy-19949 and http://www.openphotographicsociety.org/shop-and-tools/photographers-rights-uk/rights-card/858-photographers-rights-card-download (very similar)