I was led to belive that tax relief was only going to apply to your main home and not other properties,

a - is this correct

b- does it only apply to additional properties outside Guernsey

c- does tax relief apply to all properties you may own on Guernsey

Any info would be great

That's all I could find. Not sure if any use to you?

http://www.gov.gg/ccm/treasury-and-resources/income-tax/website/publications/states-reports/land-property-and-interest-relief.en