Define budget ? How much are you willing to pay for a hotel room ?
The definition of budget is a very relative idea.
I always get one night offsite when I go to WDW. I book it through a TA as part of a flight+hotel package, as it often ends up being cheaper than booking flight + hotel separately.
Some TAs will allow you to have hotel stay dates different from flight dates. But I guess it won't matter to you.
Anyway I always spend my first night in Clarion Inn Lake Buena Vista.
Nice clean rooms, just off I4 (can get noisy if room is facing the interstate). The rooms are pretty much like the rooms at Disney's values, except they have fridge, microwave oven and coffeemaker. Restaurant onsite (breakfast buffet for $8 with usually a buy one get one free, length of stay voucher at check in, so 2 adult very hearty breakfast for $8)
It's on palm parkway, very close to the entrance of the "mickey zone" (as my son calls it) north of Downtown Disney and hotel plaza boulevard.
Restaurants within walking distance include Cici's Pizza, Sizzler, Pizza Hut, Denny's, McDonalds, Burger King, IHOP, Olive Garden, Domino's Pizza (and many others, plus Domino's delivery at front desk)
rates for february are at £55+tax (12.5%) for a standard room (2 queen beds), and there is a special rate (non refundable, non exchangable, advance payment, need to signup for program) at £47+tax
That's how low I'd get as far as budget.
You can find better deals looking at things like Motel 6 at Main Gate in Kissimee. (off US192) at rates as low as $36 per night (+13% tax) but I'd personally avoid that. Not the hotel per se, but the US192 area which I consider to be a cutthroat for foreigners at night. That's the kind of place that makes you feel uneasy when you realise that your foreign accent paints a wide "tourist" target on your back. DW who only speaks french didn't dare speak to me the whole time we were waiting for a pizza outside of pizza hut, too many weirdos and winos and probably some pushers too. I bet strong british accent would have the same effect.
Also consider that you'll have to deal with transportation, and that hotel shuttle to parks might be painful and stressful to deal with.
Some operate on limited schedule and if you miss your shuttle, it's taxi full fare and nothing else.
for budget but reliable airlines, I always go with the big 4s (AA, US, DL, UA) they're not really budget, even though shopping around can get you great fares. We saved over £200/250 per person just by selecting a flight schedule and looking every morning on the internet until discounted seats were released. 2 days later price had gone up £200, so it's also really hit and miss.
