Is it possible to filter collections items by price?

For example, if I have 200 items ranging in price from £1 to £200, can there be a slider that can just show £1-£50 for example, or £100-£200?

If you enter your prices in a Number field in your Collection, then you can perform all sort of filtering on that field. In your case, you can filter on a range:

As for the slider, what you can do, depending on how many ranges you want to propose, is to use a Tab element. Each Tab item is a range, and the first one is for All. Inside of each Tab Content, you place a Collection List that is filtered on the appropriate range. In the end you have a row of buttons instead of a slider.