Correction: EU, not UK. It's still nonsense, but there are signs that the European Parliament is recognising that fact. I've not flown this summer, but is Spain (and possibly others) still asking for passport numbers and addresses to be registered with the airline in advance of check-in?
WRT to the OP and UK customs: I've bought various bits of computer kit from the US during the last ten years. All of it has been "vintage" stuff, and 90% of the time this has been recorded on the customs declaration. Strangely enough, all parcels were sent by USPS so the deliverer in the UK was Royal Mail or Parcel Force. The price that I paid for the goods was between £10 and £500. In total, probably 15 or 20 parcels.
During that time, I have been asked to pay customs duty three times. Other people are less lucky, and large, professionally packaged items are a popular target for customs. Customs duty is a stinker: you pay an inspection charge, which varies depending on the value of the goods and the carrier, but it is at least £5. On top of that, you pay the import duty -- it varies depending on the item, but just use VAT as a starting point.
In the long term, it works in your favour. Occasionally, you get a silly bill before you go to collect your parcel, but it is very unlikely on a small package of SIMMs.