Upvote:2
This is common for many countries for visas, and the frustrating thing you realise is - there's no set amount of money.
Generally, you need to show you have 'enough' for the duration of your trip.
So this might include a letter stating you've got accommodation sorted (staying with friends/family), plus money to show you can cover yourself.
What they're looking for is evidence that you've thought your trip through, including emergencies, contingencies and have worked out and have evidence of funds.
If you're being supported by a family member, you're still going to need evidence of the funds - otherwise they have no way of knowing if it's royalty or a broke cousin that's supporting you.
From one such online British document detailing what to provide:
If you are not funding your stay yourself, the person who will fund it should consider supplying the evidence
I suggest having a read of the document for further information as well, but essentially, the responsibility is on you to convince them that you're not going to end up in financial trouble while on your visa in the UK. Frustrating :/