Rut, I've owned both a Midget and two Spitfires. If you're out for a good sports car that is particularly British, just about any MG or Triumph will do. My best advice is to test drive them, and see how they fit.
The Spridget cockpit is snug, but if you're average height or smaller you'll fit fine. Some folks don't like the steering wheel quite as close to their chests as MG's have it, but I found the Midget's ergonomics very comfy. I'm 5' 7" and with the seat all the way back I fit perfectly. The short doors make for some real leg folding to get in or out, so be sure to try the car on with the top up to be sure you can fit in and out.
The Spitfire cockpit has narrow seats, but more knee room. The steering wheel is further from the driver because it was designed by an Italian. Since you won't be racing, the best car is probably a 1500, which has more torque and more power. Get an overdrive if you can find one. I liked the overdrive so much that I put one in my Midget 1500 (and it wasn't easy, but it was sure worth it). My first Spitfire was a Mk. 1, which was a delightful car to drive. It would occasionally snap into oversteer in tight bends, and my Spitfire 1500's "swing spring" rear suspension totally solves that problem.
Here's were I should brace for flames: if you're looking for a fun and cheerful sports car and don't care if it is British, get a used Miata or MR2. Both are very reliable and very fun to drive. First gen Miatas and first gen MR2's both handle "British"... the Miata because the Mazda engineers really wanted the holistic British sports car experience, and the MR2 because it was designed by Lotus to be an entry-level Lotus with Toyota mechanicals, but in the end they decided they couldn't handle that sort of volume so Toyota took over the project and sold it as a Toyota. If you've got more money to spend on your sports car fun, look into the BMW Z3. I drove one for a day a few years back, and it was everything a big Healey is plus reliability and all the modern comforts.
I'll also go out on a limb and recommend the TR7, at least after you replace the suspension bushings with new ones. Also, if you want cheap American parts available in any auto parts store from sea to shining sea, look into the Pontiac Fiero. The later ones handle very well indeed. Of course, it's harder to get the wind in your hair with these two cars.
Myself, when I went to look for a thrifty, fun commuter to prepare for this summer's coming $4/gal. gas prices, I looked for a Spitfire 1500. I've been driving it 60 miles round trip every day for two months very reliably. It's been very reliable despite sitting under a pile of pine needles for five years before I bought it.
Scott