Applying for a 0% purchase card

Hi all

Looking for a quick bit of advice please.

I currently have one credit card with £385 on (limit is £2,450) - I have been paying this down each month and it will be cleared in the next two months.

I want to apply for a new credit card which will be 0% purchases to buy something that is about £500.

On my eligibility on this site, the best deal is only giving me a 95% chance of approval with Virgin and MBNA.

On U-Switch, it is giving me a 100% chance with Virgin - all information input is the same.

I've been on the Virgin website and their check pre approved me. I've read on here that this doesn't mean a lot and that even a pre approval can be turned down?

What should I do? My credit history have improved over the last year, I don't have any hard searches so I am a bit anxious about adding one and being turned down.

Thanks.