Having trouble getting a loan, probably due to circumstances. Any help appreciated?

Ok here goes: I'm 19, and am in the process of purchasin a house with my Mrs. I need a loan for about £5900 (to pay off over about 6 Years at £105-ish a month) to pay the deposit. I've 2 Credit Cards (with a total of about £1000 on) which I've never missed a payment for, I also have an overdraft... show more Ok here goes:
I'm 19, and am in the process of purchasin a house with my Mrs.
I need a loan for about £5900 (to pay off over about 6 Years at £105-ish a month) to pay the deposit.
I've 2 Credit Cards (with a total of about £1000 on) which I've never missed a payment for, I also have an overdraft of £750 which I use alot at the minute, mainly to pay the credit cards off.

I've applied for 3 Loans in the past week and have been rejected for each one. Using Equifax, my credit rating is "GOOD", so I don't understand what the problem is?
The first 2 loans I applied for were for £8000 (so I could pay off the overdraft/credit cards too), maybe that's why I was declined for the first 2?

If any body know a decent Building Society/Bank/Whatever who will lend me £5900 for a deposit, I'd be extremely grateful if you could tell me. Alos any advice would be much appreciated.

Cheers
Update: Thanks for your answers so far, just to add I Help fund my Mrs. Apartment (as she had issues at home). And the reason I'm in debt at the minute is because I've already paid £1250 towards the house, and we went on Holiday a few months ago.
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