If the lappy itself still does all you need it to do but slowly then buy a cheap SSD £25 fit it and do a fresh windows 10 install, save yourself some money, also maybe upgrade the memory if you can, 4gb sticks are about £20.
My concern at 11 years old would be a dates processor, but yes, as Peter says, if the load isn't too taxing you could probably get it up and running to a decent standard for between 50-100 quid.