Suppose it depends on your dress sense and where you will be hanging out. The price of basics in H&M or Primark is often less than a tall skinny latte at Starbucks (and certainly less than hotel laundry per item), so T's, socks, and pants can be brought, worn and then junked or (preferably) donated to Oxfam or Fara. When I visit the UK with my kids, we go with no baggage and buy what we need on arrival. They play in the mud in Richmond Park!