Will Barclaycard charge me interest?

Hi All,

Please help me with the following question if you have a barclaycard or understand the way credit cards work.

I hardly ever use my VISA Barclaycard, infact, I probably have a £5 balance on the account. I don't know much about how credit cards work. I know I am allowed to go over £2000 (credit limit). A couple of days ago, I had to purchase something urgantly for around £280. So I must be around £275 in debt to them. I can pay this no problem, just don't have time to go to the bank for a while. Could someone please tell me if they will charge me interest, if so, roughly how much per day? If not, do I just get a bill for this exact amount at the end of the month which I can just pay online?

I don't want to wait ages only to find they have charged me loads on interest.

Thanks in advance. I feel silly asking this.