Absent tenant needing car and belongings storage

Unusual search here. My wife and I live and work abroad but need a place to store our UK stuff, including a Chrysler Town and Country minivan and BMW motorbike on SORN. An empty room with off street parking and infrequent mail essential. We visit UK 1-2 times per year, total of about 2 weeks, so would visit occasionally but likely not stay over. 500GBP per month is top limit really. We can pay 6 months in advance if necessary. Bristol-Bournemouth-Exeter region. Village or larger. Regards, Neil and May.