Hi. I'm a UK dvc member, who did finance direct!
First thing, you really do need to understand how it all works before making any decision.
Second, I'm more trying to answer the general "is it worth it" question. Others are giving you the financial info so I'll stick to the wider picture.
So you know how often you want to visit and how much it costs by booking a package. Now where do you stay with a package and where do you want to stay in future? Our first stay onsite was at the Beach Club, us and 2 teens/tweens in a room. No way did we want to do that over and over. We like a 1 bed villa with kitchen, separate bedroom and a washer/drier. So that means a luxury resort.
How long do you see yourself going? Not 14 days every 2 years, but how far into the future? 10 years? Well you'd only just have paid it off by then, Little point buying. 20 years? OK, maybe worth it. How much would it cost to rent a studio at the Poly? Flights and park tickets need to be bought each time, so it's only the accommodation cost that counts.
But this is not a purely financial decision. It's about having the accommodation for a holiday for 40+ years for the price of the annual fees, once it's paid off.
We own at BLT, annual dues around 700 at the current exchange rate. Last year it was 500, and that's not all due to the price increase, that's the pound plummeting! And that will affect your decision. However depending on when you go back maybe things will change. Because to finance it through DVC you will have to be in the US as it's a bank loan (think second mortgage).
We only plan to go every 3 years at the moment, so bought accordingly. How many points do we need for 2 or 3 weeks BLT at peak season (school holidays) divided by 3. When we can go more often we can go at off season times so the points go further.
Fianancially, comparing the cost of paying to stay in a villa against the total amount of the loan plus dues for 10 years, puts us at just about breaking even on our 5th trip. (That allows for the dues for each year after the loan is paid off). so that's after 15 years. Certainly by the 6th trip we will definitely be "winning".
It would be worth looking into buying resale, but if you need to finance I think it would be difficult to get a loan to buy a timeshare, albeit one that holds it's value well. Also I have no idea how easy or difficult it would be as a UK citizen, from a tax perspective.
Hopefully this gives you some useful things to consider. Do you want me to look up the points for a studio stay at the Poly? If so, when would you be travelling, roughly?