"To go" versus "to take away": that matches my much scantier evidence, yes. My relevant visits were in 1997, 2001, 2005--2001 was for a whole month, thanks to a research grant and sleeping with a loaned Toshiba laptop in a crowded hostel. In 2001, I had to say "for takeaway" or get the stinkeye between St Pancras and Bloomsbury. In 2005, sometimes the person ringing me up gave me a second look and asked whether I wanted my meal to go. (They couldn't always get it from my accent--I blend, partly consciously and partly not.)

Between 2001 and 2005, speaking of takeaway, there was a steep increase in the number of Pret a Manger shops in London in kind of a triangle made by Euston Sq, Covent Garden, and Oxford Circus. I was still able to eat sandwiches at the time, and it was markedly easier to feed myself in 2005 than 2001 without sitting down at a pub or for a full restaurant-style evening meal.

(I went outside London for all three trips, but London has my clearest memories of planning meals.)