Hi,
I dont know if this will help as you have stated you are after finance. However I recently purchased my air rifle from Woody's of Wembley who advertise in 'Airgunner' and 'Airgun World' and they use a system called cheque spread. Basically you send six pre-dated cheques and they withdraw the money on the dates the cheques have been written for, plus this way you don't pay interest! Hope this helps.
James.