Hold you up. You mean it takes you an extra 30 secs to get somewhere.
Well done for quoting a dictionary perfect definition of holding you up.
If I was out in my car and slowed to a speed that held up cyclists, they would be gesturing me to get out the way as well. Simple fact is Cyclists are the slowest moving road users and to go 2 abreast, uphill, to maintain a conversation with no regard to other road users is selfish and contrary to what the highway code suggests is good practice.
If the driver had to speed past close to the outside cyclist he would have received abuse as well. In this case he correctly indicated his presence and gave to cyclists the opportunity to move to a safer road position. As a result he was verbally abused. Much like the lorry driver in the other cyclist thread who tried to indicate it was unsafe for the cyclist to pass (allegedly).