I originally wanted a K&N but they were not out when I got the Trust one (recent LOC GB) - the K&N came out the same weekend I tried the Trust - took it out and ordered K&N - still brand new except for 10 miles use - no real reason - just me being me I guess ! :P
No not declared on insurance - as it fits within the standard airbox it is not altering the performance of the engine any more than changing a dirty std filter for a new clean one IMO.
Have declared TTE springs but would not expect panel filter to be an issue - unless you folks out there know different of course ?