airbanda is quite correct. In the UK (and that includes the IoM and Channel Islands) it is legal to listen without a licence only to authorised broadcast stations, amateur stations and stations in the 'Standard Time and Frequency Service.' I expect GPS is counted as a 'broadcast station'. Licence exempt operation (cordless and mobile phones, garage door openers etc) only allows the reception of messages intended for the recipient. Reception of communications by accident is covered by a confidentiality clause in licences.
The only 'exception' to this is that any station receiving a distress call (MAYDAY)has a duty under the Radio Regulations of the International Telecommunications Union to afford such aid as may be possible. I don't think that is on the RA website, though.