suzey,
I'm not sure what the winter weather is like in your neck of the woods, but where I am, winter tyres do make a lot of sense. I'm originally from Dorset and if I were still living there, I know I wouldn't bother with them because in all the years I lived there right next to the sea, snow was rare, ice wasn't really a huge issue because there was enough salt in the air and on the road for it not to cause a real problem.
I personally wouldn't buy two new winter tyres leaving two 'summer' tyres on. If you are going to go down the road of using winters, I'd recommend them all round and buying a complete set of winter wheels from mytyres or similar, so you can just swap from summer wheels to winter wheels when the time comes. Some people don't have the storage space though, but if you have a garage, then it shouldn't be an issue.
If you just end up sticking normal tyres on the car then there's certainly a choice out there. Three months before we got rid of our old POP, I had to buy two new tyres for it. I bought a brand called EVENT. They were £35 each fitted/balanced and they went on the back of the car. We had no issues with them whatsoever. They were 2013 stock and what I mean by that is, when you do go to buy new tyres, ask to see the manufacturing date code on the tyre. Ideally, they shouldn't be any older than six months from manufacture. If the tyre shop you use is decent, they shouldn't even quibble about it, but whatever you do, don't be fooled or fobbed off into parting with money for rubber that is over 12 months old because that just indicates a slow stock turnover.
Dont' forget too, tyres do need a couple of hundred miles wear in period. People forget that, so no hard braking, be careful in the wet etc.