You haven't got a chance of importing more than the guidelines with a white van - you're going to get pulled in Dover regardless. Even importing the guidelines in a white van is dodgy.
If you want to import those things, pay the tax - but you've got no chance of making any profit with paying not only UK excise tax, but Polish excise tax too.
she exports to France and there is NO duty on good, not there should be any for other EU countries.
There is no duty, but as I recall, you still have to have some paperwork showing where the goods are being exported and imported to - it's not just as simple as loading a van with goods to re-sell.