Focus 1800 Intermittent Idle Issue

Hi,
My year 2000 UK Focus has developed an intermittent fault.
Normally it's when the engine is warm, and I've been travelling above 60mph.
When I take my foot off the accelerator, the car will keep going at
roughly the same speed. If I dip the clutch, the engine can race to as high as 4000rpm.
Could this be the ISCV I keep seeing references to?
thanks in advance Phil
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