As I see it if the sign says 'except Bank Holidays' or 'Mon -Fri' you should be okay (providing they consider 26th a Bank Holiday as officially it seems to have been moved to the 28th)
The on-street, off street 'pay and display' charges and controlled parking zones (excluding the Twickenham Event Day CPZ) do not apply on public and bank holidays
Yellow lines and loading restrictions are an in force during the times shown on the relevant sign, even if this falls on a public or bank holiday
Like yellow lines, bus lanes, disabled bays, bus stops, taxi ranks and loading bays are in force during the times shown on the relevant sign, even if this falls on a public or bank holiday
Footpath parking restrictions and white pedestrian crossing zig-zag restrictions apply all day, every day, including public and bank holidays
The council is closed on public or bank holidays including the period between Christmas and new year
Christmas Eve 24 December - No charges will be applicable in London Borough of Hounslow controlled paid for parking spaces on-street and in car parks.
Bank Holiday restrictions apply on these days - 26 and 28 December and 1 January
Please note: normal restrictions apply on the following dates:
Sunday 27 December
Tuesday 29 December
Wednesday 30 December
Thursday 31 December (New Years Eve) and again from Saturday 2 January 2016
Motorists should note that other parking restrictions such as double yellow lines will still be in place and will be enforced during this time.