If you visit www.surinenglish.com and click on the classified ads links on the left hand side of the homepage, then on the insurance link, all advertisers for insurance as advertised in the latest edition can be found. Most of the larger names advertising tend to have a website of the company name ending in .com which may make the task of comparing prices rather less expensive than phoning any advertised numbers.
Beware of any small print in cheaper quotes which could affect the validity of any claim. Some cheaper policies tend to have small print which can dictate quite strict conditions if the property is left vacant for any length of time (often as little as 7 days!).
I insured my property with my bank as johnone has already suggested and would be reluctant to change away from LloydsTSB as the level of cover is very high with very few conditions attached.