I'm not in the UK either. It looks interesting, I assume you are looking at the Digi Gold? You might want to see if there is an ETF available for gold and compare the expense ratio.
It looks like they sell physical gold too, I saw a James Bond bar, it is listed as a popular choice hahhaa. I would want to know if they will buy metals back or if you have to find a local dealer to sell to.
Personally I don't invest in gold, I did back in the 1980's and it took me around 20 years to recover my losses. I do have some collectable coins just because they are nice to look at and have in your hand as a part of history.