Citroen Xsara cruise control 'fault@

I have a recurring problem with my CC that appears to have everyone baffled. I have the CC on, and the radio, and all is fine except, sometimes and only at exactly the same place on the road I get a warning beep, the engine management light comes on and two messages on the display 'Cruise Control Fault' and 'Engine Fault'. The first time it happened it reset itself before I got to the garage but they checked, no error codes anywhere. The second time all error messages and warning lights on but, again, no error codes anywhere. They reset and it is OK up to now. (I didn't get charged for either check as no fault found). My theory on this is that at the exact point that the error occurs, it is on the brow of a hill and comes immediately into line of sight with a 290m high TV/Radio transmitter, blasting out up to 200kW of VHF and UHF signals, and that my car aerial is picking up a stray signal, putting it through the radio, dash display and feedback into anything else switched on, which happens to be the CC. With the multiplex system on board it could be a possibility. It has not been wet or raining when this has happened either. Has anyone heard of this? If so, is there an RF filter available to fit into the aerial lead? I have sent all the details directly to Citroen and they are having a look, and local main dealer is doing a check and software update as well.