But being fashionable doesn't have to mean that you buy a new closet for every season - you can easily just combine your old stuff in a different way than before. I also fix my clothes a lot to keep them longer - that's why I've bought a small sewing kit from Sainsbury's. Moreover, what also helps is if you keep cleaning your closet often - this way you are truly aware more of all the pieces you've got, and might get inspired. Taking care of your (even old) clothes and keeping them in nice order is the key for saving money. Obviously it would be nice to be able to wear luxury brands and buy new stuff every week, but as we know for many student's (especially in UK) this is just not the reality.
When you go mid-season sale shopping, remember this: The real price of the item is not the one in the tag. You will get the real value of the item by dividing the price by how many times you wore the item. In this sense, if you buy something 'expensive', but wear it on daily bases, it was eventually 'cheaper' than some bargain you ended up wearing once and paid 10 pounds for. I also try to keep this in mind, because it's often tempting to buy things just because they are cheap.
Hoping these small tips helped...Have a good Friday! :)