Hi Liz B - Welcome to the forum. I imagine there are lots of people who have withdrawn cash on a credit card to live on in the run up to BR. I wouldn't specifically draw out £495 as I think the OR might not like it. See what the other experts advise - I have recently gone BR and saved the money up over three months - they may suggest you save it up over a period of time rather than make one withdrawl. A BR assist expert wil be online soon.
It's a tough one to call. Suffice it to say, it is usual for everyone to exhaust all lines of available credit prior to going BR. Therefore, if you make a few withdrawals, I'm sure you'll be fine.