Wonderful news about the clear lungs, scrumper!
Toning really should help - but please be very careful if you're having breathing problems, especially if you intend to do any cardio.
Pilates is very good for toning, but I'd highly recommend that you attend a class at first because you really need to get the correct breathing and positioning (helps prevent injuries and makes the exercises so much more effective). Then you can buy DVD's to use at home whenever you want. Varying them is good, so that your body doesn't become too used to one particular routine. I find the Stott Pilates series to be excellent, and they're great at helping you with performing the exercises correctly. They're available on amazon - but be sure to choose the DVD Region 2 version for playing in the UK, otherwise you'll end up with North American Region 1.
Walking is good for toning the legs. You can do it outside, but there are also "in-home walking" DVD's. These combine walking with exercises and can be pretty effective. I'm currently using a Lesley Sansone DVD called "Walk Away the Pounds: Ultimate Collection". It has 4 routines - 1 mile, 2 miles, 3 miles and 4 miles. This involves brisk walking, incorporating various exercises whilst walking and the use of a resistance band (one was included with the DVD I bought). So you can build up as your stamina improves. Also great for bad weather days when you might not fancy walking outdoors. Again, these are available on amazon - but only for Region 1 (North American), which you will only be able to play in the UK if you have a region-free DVD player.
Exercises such as squats and lunges are also great for toning legs and buttocks. Be sure to always warm up and then stretch afterwards, though, so that you don't injure yourself.
ETA: I've changed this post as I forgot to mention the DVD regions.