I have thought about upgrading from my free account many times and would be happy to pay the monthly ammount. however I cant afford to pay the whole 12 months or two years in one go up front. If I could commit to a month by month basis as a pay as you go option I would almost certainly have become a full member by now. Perhaps you would Greatly increase your revenue if this option was available.
Second suggestion is a paypal option. In the UK the use of credit card information over the internet is considered insecure and hands control of your finances over to the vendor. Paypal on the other hand keeps control with the purchaser. After all having to commit to a long period up front suggests to the customer that you need to trick them into a commitment and so there must be something "Dodgey". These two financial options would significantly gain customers which are currently being missed out on.
Finally the free 14 day trial forces the purchaser to give financial credit card details up front and so if the trial is not as good as was expected, its too late to change your mind as the vendor can charge my credit card at will. Again customers are too internet savy these days to take that chance.
Food for thought perhaps
Kind regards
Pete Ormroyde