In the weather that you are having in England I can't explain how important it is to warm up properly before doing any type of exercise.

This will seriously decrease the chance of you damaging a muscle etc.

Upper body strength will help your running a great deal. So doing situps and pressups will be of great benefit to you.
Pick a number that you are happy with (say 15) to do and then have a rest and then do these in repititions.

Say on week one that you will do 4 sets of 15 each night of situps and then 4 sets of pressups. Then on week two you will do 16 in each set.

Getting fit is about many things from what you eat, when you eat, how much sleep you get etc.

As Damo has said. If you can find a friend to go running with then that will help a great deal as you are less likely to walk and more likely to push yourself.

If not then I find that putting some tunes on your mp3 player that get you going really helps.

I listen to old skool like Ratpack (waits for the piss taking ) and that gets me going.

Pick an interesting route to go. If that means that you drive to the park and run round cos the surrounding are you live in is crap for running then do it.

Write on your calendar when you exercised as it will make you guilty if you haven't gone out for a couple of days.

Make a chart of your results and run times. It makes it all seem worth it if you are doing more of the exercises and the run times are getting quicker.

Not saying you have to but I take a multi vitamin and cod liver oil tablet each day. Probably just a psychological thing

As for running trainers , there's no need to spend £80 on a set of expensive trainers that might not be designed for running.
Asics are a very good make of running trainers and not expensive either

Lastly. I cannot emphasise how important a real good stretch off after you have exercised is. This can make a hell of a difference as to how sore you may feel later on or the next day

Stretching doesn't have to hurt as a little makes a big difference.

Hope this helps a little