Duplicated from another item.
A couple of months ago I bought a Delta 3 radiator grill and four hubcaps from a French dealer and had them delivered free of charge to my neighbour in France. I then used parcelbroker.co.uk (no connection to me) who provided the delivery label and customs declaration label for me to fill in. Paid them around £25, emailed the labels to my neighbour, the parcel was collected next day and with me in four. No demands for any extra payments. Yet!
We have also for many years brought back from France old furniture clocks etc and have checked what the customs situation might be now. It appears that we fill in a simple customs declaration on line which calculates any VAT or duty due. Submit the form, pay the VAT/duty and use the "nothing to declare" lane at the UK port.
There are limits on things like alcohol and tobacco, other items up to a value of £390 are free.. I presume (hope!) this is per person and not per car?
https://www.gov.uk/duty-free-goods/declaring-goodsRobin.