in regards to the letting people in situation... if there is a car between you and the car in front trying to get across and they indicate to come in, you should ALWAYS drop back to let them in. but only one car. if another car tries to push in, it is acceptable to block them off.
in regards to waving... if you've let someone in and they do not wave. then it is acceptable to get the ****s and try and ram them off the road. by the same token, you should always wave when let in to ANY gap... even if it was a tight gap that you slide into without the other driver going too much out of their way. still wave! its nice and takes you like .02 seconds!
ALWAYS WAVE!
and about cyclists: they have every right to be on the road, and if they are good cyclists, they wont cause too much disruption on the traffic. if they are crap cyclists, then they are asking for an accident happen. im so scared of cyclists cos ive had a couple just whiz across in front of me in traffic, and ive had one fall against my car at the lights. the retard couldnt get his foot out of the thingos and just fell on my car <_<... anyway if you hit a cyclist its ALWAYS your fault, and you will get chewed by the legal system, even if its clearly bad skills of the cyclist