How can I fix my Rover 216 coupe 1997 ignition problem ?

Recently an intermittent ignition fault has developed as follows:- The car will start first turn of the key but as it warms up it runs a little 'lumpy' then after it has been driven a short distance the ignition will suddenly cut out but will cut back in again if I pump the accelerator pedal. This 'cut-out' usually occurs when the car has been brought to a temporary stop such as traffic lights or junctions then as I go to accelerate away the ignition just 'drops out' untill I pump the gas pedal to get it firing again. I checked the distributor cap and discovered that it was well worn so I replaced it with a new one. Problem still there, took it to a garage for M.O.T. (which it passed) and on the advice of a machanic had the 'air intake electronic control valve housing' cleaned out as they thought it could be a sticking control valve, drove from the garage and problem still there. I'm loath to take it to an auto-electricion as this could be costly and I intend to sell on the car and don't expect to get more than a few hundred pounds for it so this course of action will be my last resort. Is there anyone out there who could piont me in the right direction as to the likely cause of my problem ?? I would be most thankfull for any constructive advise offered up. Thanks in anticipation, Proffo (Roy).
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