). The UK's one also has some oddly worded bits (IIRC it asks "Country of issue" for passport but the answer probably for most of us is "British Citizen"!). There are instructions - the UK's runs to around 35 pages although oddly doesn't cover all the stuff, but thankfully you should be able to figure out the missing bits. The Spanish instructions are only around 20 pages and a bit clearer! 
We've just got back from Mallorca, travelling with First Choice (part of TUI) - presume the same for you? - and also used the Chronomics £20 deal for LFT within 72 hours of your return flight, and the PCR on day 2 of return. With FC/TUI Chronomics tests you can get the results quickly by taking in to a participating TUI travel agency - I dropped mine in to the one by the clock tower in the centre of Brighton late morning on Monday, by early evening the lab in Nottingham confirmed receipt and that they were working on them, and the next morning had the results. Nice and straightforward. Quicker than posting them through the Royal Mail (they DO come with an post-paid envelope to post them back in).
The paperwork side of things is laborious but actually not too bad. The Spanish government's Passenger Locator Form website is better than the UK's - if travelling as a family/group, you can add all passengers onto the same application, but the UK's PLF insists each person completes their own separately (or muggins does all of them while everyone else is in the sunshine enjoying themselves!
Echo the value of having the LFT result printed out, along with the UK PLF for each person (just the first of the four pages you get for each person, as it has a QR code). Also everyone have the NHS app to show your Covid vaccination status too. Seems like most of the checking is being done at the check-in desks for the airlines; when we got back to Gatwick we breezed through the eGates with nothing else needed/asked for. I have a feeling that hotels without Business Centres are now very used to printing things off for their guests these days!
The Madeira entry stuff is brilliantly efficient, as is arrival. No queues and took no more than a minute or two, and registration for their locator was easy.
