It's not too often that I have to pull out circuit breakers, as an upgrade is usually to replace an old panel with rewireable fuses (breakers having become common in domestic panels here only in about the last 20 years or so).
I'll generally ask the owner what he wants to do with the old stuff, and 9 times out of 10 he just says "Take it away."
Any of the fuse carriers which are still in good condition I'll keep to use as spares. There are still hundreds of older Wylex and MEM panels in service around here, and it's handy to have a stock of spares for damaged or wrongly-sized fuses, especially the MEM type carriers which went out of production years ago.