Thanks for coming back to me. I have had the diagnostics done (again) and there are no error codes being reported.
The light that comes on when the engine stutters is actually the orange imobiliser light (bottom left hand side of the dashboard window).
The local garage think the problem may be something to do with the imobiliser circuit.
I have two keys and it does it with both, so it is not a defective chip in a key.
Is there any way to bypass the imobiliser just to get me out of a hole, if that is what it is?
How do I find someone who has the necessary kit to do the immobilizer diagnostics?
My local guy only has the equipment to look at the ECU and all the engine management stuff.
There is a Suzuki dealer in Newbury. Would they have the kit to do this?
The earliest I can organise this now is Monday.
I have found the answer. You were right, it is the crankshaft sensor. Apparently the fault does not show up on the diagnostics with an error code.
I am sorry I only rated you OK, but you were hassling me for a rating and I did not know you were right until just now.