Paul,
don't forget anything that is designed to cut will also require sharpening, so your budget will need to include this facility if you don't already have it. As a confirmed power tool user long before I came to appreciate the black art of handtools I know only too well how easy it is to overlook this.
As to your planes you're right to think block plane, it certainly is what I use most often. I love my Veritas low angle one, but the cheap and cheerful Stanley 102 gets used a **** of a lot for basic stuff like just easing corners, fitting back panels and the like. And I can toss it in the toolbox with impunity for out-of-the-workshop stuff, which I wouldn't dream of doing to the LV.
A smoother or jack plane (or both) should be aqcuired early on also. No need to spend lots at this stage, the lessons you'll learn making a cheap one cut well will stand you in better stead than going straight to Clifton or Lie Nielsen at this stage. DON'T buy secondhand from Ebay, there are some good planes to be had there but separating them from the piles of rubbish is an art all in itself, you'll likely have to buy 3 to get one worth fettling even. Good ones there rarely go for bargain prices anyway - it's not unheard of for s/h LNs to change hands for
more than the new price - go figure, as our US cousins say.
If you fancy older stuff you could do a lot worse than
Ray Iles who does a nice line in s/h Stanleys with reground soles.
Careful on that slope though, it can
really slippery :wink: