You are not comparing like with like.
IMHO you should compare DVC with other on-site prices not off-site villas.
The cheapest room in the Grand Floridian would cost about £2,870 for 2 weeks in Oct according to Expedia.
Again checking on Expedia, you could rent a studio at OKW or SSR for £2,125 for 2-weeks in October; a 1-bed would cost £2,870; a 2-bed would cost £4,020.
There are ways of minimising these costs by renting points at $11 or so a point from existing DVC members instead of renting on a cash basis.
Whichever way you do it though an off-site villa will always be cheaper.
The alternative of course is to buy DVC and then your cost (excluding the purchase price) is the annual maintenance of +/-$4 a point depending on resort. So, assuming from your post you need 450 points it would cost you $1,800 (=£973 @ $1.85:£1). The difference between the £973 and the cash prices shown above is how DVC owners calculate their pay-back time for their DVC membership.
Happy planning
