please see this link
https://www.securitywarehouse.co.uk/catalog/index.php?main_page=advanced_search_result&keyword=grade+AND+3+AND+flush&categories_id=44&manufacturers_id=&pfrom=&pto=&dfrom=&dto=
Both have good wireless options but id be wary of anyone giving away apps for free etc. These things do cost to run and often the free ones have less reliability.
I must admit nor me. If the fuse is in tact I'd check the trace. If you meter on other ground etc do you get a reading. I cant recall but are these power connectors on plug on blocks?