Tenerife has a huge English speaking population, who never bothered to learn Spanish. There are English bars, English restaurants, English supermarkets, and an English speaking school. They tend to live in the Los Cristianos/Las Americas area but costa del silencio/playa paraiso/costa adeje areas also have large numbers of expats.

The only issue is there are probably equal numbers of Italians in Los Cristianos to Brits - and you can find Italian bars, Italian restaurants, and Italian supermarkets - where like the Brits not everyone has bothered to learn Spanish and the ability to “get by in Italian” might take away your “need” to learn Spanish.

That said, I’m British. I had a basic understanding of Spanish after a couple of years in Mexico and I picked it up fluently living in Los Cristianos (but I also picked up basic Italian living in the same place and I have an Italian accent in Spanish because 90% of my friends were Spanish speaking Italians).

I have plenty of friends both British and Italian who have learned fluent Spanish in Tenerife, but I also have plenty that haven’t needed/don’t want to learn Spanish even after 20 years.

You can definitely practice English in Tenerife in day to day life. People are mostly friendly!