I think the term "collapse" is a bit problematic.

In terms of land area the British Empire began to shrink from its peak land area in 1921.

For the next 50 years you see a steady change in the status of areas previously within the British Empire. There are one or two big changes along the way (India in 1947, "Wind of change" in Africa in the early 60's) but you don't really have a year or even a decade when you can say "the Empire has collapsed".

I mention this because in as much as the residents of the UK had a view on it at all it was necessarily a changing view due to the extended period over which it took place.

Hi, I wrote a reply covering Communist Party of Great Britain attitudes in response to a similar question about a year ago accessible here (btw fuck hyper linking on mobile...) https://reddit.com/r/AskHistorians/comments/3p99ra/how_did_facets_of_the_british_society_reacted_to/ It's a little lengthy and specific but will hopefully be of interest

In terms of "general public" reaction (personally I don't think such a thing exists but am willing to accept that others do) beyond the CPGB I sadly can't speak much to that. I would note however that generally other than on the political extremes, decolonisation wasn't generally seen in newspapers I studied at least as a "collapse" as such due to the largely planned path taken, but this is more a semantic point.