OK, so this is my final decision. Honest!
I'm getting the electric wheelchair I saw first (the Aries that goes 25 miles per charge) to walk Mitzi then save up for my ideal chair (the Lugano which goes 20 miles per charge) after that.
Why did I choose that? It's £200 more expensive than going with the 6 miler (the Capricorn)!
The main reason is that I would only need to charge the Aries up once a week, it goes 25 miles on a single charge and I can stand up temporarily when I need the extra height. It will also mean that I can get used to being out and about alone again. It also folds up and the battery charges up offboard which is great for our narrow hall!
I've also bought several extra things for that chair and I've got my eye on a security pouch which wouldn't work on the Capricorn or Lugano from the picture I've seen of the Aries!
The only very minor negatives of the Aries and Lugano is that they both have pneumatic tyres which could leave me stranded if I get a puncture! I'm going to email Lloyds Pharmacy about getting solid tyres on both of them so that I don't have to worry about it!