I want to buy an app costing £5.89 but I can only credit multiples of £5 to my account!!!!!

I started using the appcenter to buy mm tracker which costs £5.89 but I could only credit £5 or £10, so I credited £5 from paypal but now I can only buy the app by crediting another £5 to my account.

Either, because I don't have any plans whatsoever to buy any other apps, if I credit another £5 into my account then after I have bought MM Tracker can I get the excess £4.21 refunded to paypal?

Or otherwise, can you refund the £5 I have already credited to my account, because I do not want to leave £4.21 in my androidpit account because I have no intention of buying any other app. At all.

I can check on that for you, but wouldnt it possibly be worth leaving on a few users just in case another app ever catches your eye?