Here's another nuance from a BrE perspective, based on Elroy's distinction in #54.
There seem to be three meanings of
a bunch of. Or, at least, there's a grey area where the two obviously different meanings meet. This is how I see it:
1. A bound cluster e.g.
a bunch of parsley, as in #61
AmE

BrE
2. An unbound "cluster", or visible group e.g.
a bunch of teenagers (='a few' as in #54, gathered together in one area)
AmE

BrE

3. 'A lot' e.g.
a bunch of cheese, a bunch of problems
AmE

BrE
I think that the situation is clear-cut for meanings 1 and 3: we all talk about bound bunches of flowers, bananas and so on, but only AmE uses
bunch of as an all-purpose alternative to 'a lot of'.
As for 2, a sentence such as
There's a bunch of teenagers hanging around by the park gates most evenings sounds perfectly normal to me in BrE
. This is because it's not a statement about the large number of teenagers present (there might only be four or five of them) but a description of their physical distribution. It describes the fact that they are gathered in cluster, gaggle or 'knot'. This seems to be an extension of meaning 1 rather than an example of meaning 3.