transit the uk

hello!
i'm residant in ireland, got 5 years residency.
and i'm travelling home soon,via london-gatwick.staying in the uk less than 24hours,do i need a transit visa?
my family will be travelling with me as well,they are all british citizens.
thanks for your help.

The UK visa regime for transit purposes is nationality/ citizenship based. You do not state what this is for you. Regardless UK policy is to allow those who have a nationality that normally requires a transit visa but hold designated 'visas' principaly category D for EU member states as well as US and Canadian permanent residents to transit the UK without needing a visa (TWOV) where your onward travel is within 24 hours of arrival at a UK Port of Entry. My interpretation of the Irish residency visa you hold is that it is in the designated visa category so you will be able to TWOV.