Where can I find low-cost UK index funds outside Vanguard?

hi guys

I've been reading up on index funds and want to start investing, but I'm a bit stuck. I know Vanguard is popular, but their minimum investment is £500 which is more than I can put in right now.

I'm looking to invest around £100-150 per month to start with, and I'd prefer something with low fees that tracks the UK market. I've heard there are other providers but I'm not sure where to look or what the fees are like compared to Vanguard.

Can anyone recommend some alternatives? I'm using Trading212 at the moment but open to other platforms if they're better for regular small investments.