Here's a quote from the DoT website:
The following is a guide to the security requirements for all passengers departing from UK airports and also provides some advice that will help passengers pass through the security search point as quickly as possible.
Key points to remember:
With effect from 7 January 2008, the one item restriction will no longer apply at certain airports. Click here for more details. The maximum size for items of hand luggage is 56cm x 45cm x 25cm per bag. However, airlines apply their own operational policies governing the number of items of hand baggage which may be taken in to the aircraft cabin.
Before departing we strongly suggest you check with your airline on the cabin baggage arrangements for your particular journey.
Where possible, put all liquid items in your hold baggage. This includes water and other drinks, creams, sprays, pastes and gels.
Liquids, gels and aerosols are only allowed in individual containers of 100ml. All containers must fit comfortably in one, transparent, re-sealable bag no larger than 20cm x 20cm (eg a freezer bag).
We strongly recommend that you take time to read the guidance below before setting off for the airport.
I was wondering whether any other PFers had any "Take a Break" style tips for sticking to these rules.