(G) Bravo annoying me!!!!!

Ive got a s-reg Bravo hlx (1.8 16v). Ive had an idling problem with it from day 1. Firstly, the car started to cut out every corner i turned. It carried on doing this till i took it to a garage, who fitted a new idle control valve i gave them. It has not cutted out since, but i still have problems.
The first is if i turn the ignition off to go out, if i come back within a certain time and turn it back on, the car will start, but the revs goes right down, as if it threatens to cut off. The car feels a bit less powerful when this happens.
Also, when i do slow down, the car will threaten to cut out as i can see the rev meter go right down to zero, without cutting out, and when the car is stationary at lights, it is very shaky, you can feel it rocking.
I dunno if i bought a faulty idle control valve or not, because theres no cutting out, just dodgy revs.
Any feedback would be appreciated like wot the cause is and the cost

Lambda sensor!! Or could possibly be the crank sensor. Do a search for lambda sensors.

Oh and mine cost £59

yeah i'd agree, crank or lambda sensor

ok cheers for the help!!!!