I've taken a look at the Gloella.com website. Its layout is identical to one that I've seen many times before when people here have asked "Is site so-and-so safe?" and I've invariably ended up answering in the negative. So that alone started alarm bells ringing in my head.
Their home page states, "For the past 4 years we have been bringing the most unique products & gift ideas to the UK". Even ignoring the lousy English ("most unique"?), I find it hard to work out how they've been trading for the past four years when the gloella.com domain name wasn't even registered until May 2020!
Further, it was registered through a company called 'Domains By Proxy', which is an anonymising service that's used to keep the identity of the registrant secret. (No legitimate company would ever have need of such a service).
The site itself was put together using the services of GoDaddy, which is a perfectly legitimate company but not the way that large businesses usually go about getting their websites designed.
Unless you can eventually persuade Santander to reimburse you, I fear that you've probably lost your money.