Oopbuy lines for remote UK postcodes and islands
Highlands and islands, Northern Ireland, the Isle of Man, the Channel Islands and Scilly: which UK lines accept them and which refuse them.
Which UK addresses the line texts treat as remote
No UK card asks for your postcode, and the estimator returns the same fifteen lines whether you live in Croydon or on Unst. The remote rules sit in each line's description.
The fullest list is in the S-Remote-RoyalMail and ZD-PY descriptions: 'the Scottish Highlands and islands, the Isle of Man, the Guernsey territory and Jersey, Northern Ireland, and the Isles of Scilly'. We map those to postcode areas in the table. The mapping is ours, not Oopbuy's: some areas such as PH, PA and AB are only partly Highland or island, so the planner marks them 'possibly remote' and asks you to check.

Lines that refuse remote addresses
Nine lines say no in writing. DDF-RoyalMail and DDF BIG: 'Orders are not allowed for remote addresses'. SF, ZD-Roymail and ZSF: 'Transportation is prohibited in remote areas'. ZX-RoyalMail: 'Remote addresses do not receive mail'. Both DPD lines: 'Prohibit the use of remote addresses and island addresses'. OopLine-P refuses isolated islands and names the Channel Islands as places without postal service.
Three lines say nothing either way: HF-EUB, HP-EMS and JB-hermes. Silence is not a yes. Ask support before you rely on one of them for a remote address.
That leaves three lines that say yes.

The three lines written for remote addresses

S-Remote-RoyalMail reads £19.41 at 1 kg on a 7-14 business-day card with the fast delivery profile. ZD-PY reads £19.90 on a 15-20 card, though its measured profile is the middle one. ZXPY-RoyalMail reads £21.72 and adds batteries, perfume under 100 ml and liquids to the list of things it carries.
Compared with the cheapest mainland line, the remote premium at 1 kg is about £4.50 on S-Remote. At 5 kg it is about £7 (£63.54 against £56.58). For a remote postcode with a battery item, ZXPY is the only line that says yes to both.
Jersey and Guernsey: two answers on one board
Here the line texts contradict each other. OopLine-P says the UK's 'overseas territories and offshore islands ... do not have postal services', naming Guernsey and Jersey. S-Remote and ZD-PY say they 'can cover ... the Guernsey territory and Jersey'.
Both cannot describe the same address. The likeliest reading is that OopLine-P cannot deliver there and the remote lines can, but that is our reading. If you live in JE or GY, pick a remote line and confirm with support before paying.
The Channel Islands also sit outside the UK VAT area, so the gov.uk rules on the VAT page may not be the ones that apply to you. Check your island's own customs guidance.

Northern Ireland
The line texts list Northern Ireland among remote places, so the same nine lines refuse a BT postcode and the same three accept it.
Tax works differently too. gov.uk says VAT and duty apply to goods sent to Northern Ireland from outside the UK and the EU, and that Customs Duty can apply to goods considered 'at risk' of entering the EU, with the courier telling you if yours are. Read the gov.uk tax and duty page before relying on the Great Britain rules described elsewhere on this site.

Addresses refused outright
OopLine-P's description goes further than remote areas. It does not accept PO Box addresses or military addresses, and it names UK overseas territories such as the British Indian Ocean Territory and the British Virgin Islands as places without postal service. The DPD lines refuse island addresses.
If your address is a PO Box, a BFPO address or a parcel locker, assume the cheap lines will not take it and ask support which line will, in writing.
