PS: This quote, about cautions, might be of interest. (The 'Act', referred to, is the Rehabilitation of Offenders Act):
"Cautions, reprimands and final warnings are not criminal convictions and so are not dealt with by the Act. So if people with cautions, reprimands or final warnings only are asked whether they have any 'criminal convictions' they can answer 'no'. Sometimes people are asked if they have a 'criminal record'. This is a less precise term, but it is usually understood to mean convictions. So people who are asked if they have a 'criminal record' may also answer 'no' if they have no convictions.
However, people who are specifically asked if they have cautions, reprimands or final warnings should disclose them until they are deleted from police records. Records of cautions should be deleted after five years if there are no convictions on the record. (In practice, some police forces may retain records of cautions for much longer than this or indefinitely.)"
Source:
http://www.lawontheweb.co.uk/rehabact.htm
Chris