Hello and welcome!
Wood and paper get eaten by bugs, metal rusts, and foam, if in contact with sunlight/UV will degrade.
I can't tell what he's asking for it, but compare with buying new against what will be a substantial shipping charge from the UK.
If you choose to build you will have plenty of time to find deals that come up from those parting with parts or entire projects. A good option would be to buy the plans from Aircraft Spruce and study them. If you find out you're not into it for any reason, you can sell the plans fairly quickly.