The Government has published the Statutory Instrument which pushed the Tier 4 regulations into UK law at 7am on Sunday.
The full legal text is here. As usual, you should ignore anything said by any Government representative yesterday and focus purely on what is written.
It is as I expected, because it is the same structure as used in November. There is no ban on travel per se for anyone living in Tier 4. There IS a ban on leaving your house, however, and so travelling the airport would be in breach of this unless it meets one of the exceptions.
As usual, you are allowed to travel abroad if you are planning to visit an estate agent or show home or view a residential property for sale or rent.
Unless you are planning to look at houses whilst away, you should have left your home in Tier 4 before 7am this morning.
Hotels in Tier 4 areas are allowed to remain open if they wish. Guests must be travelling for work or for one of the other reasons stated, such as moving house or to attend a medical appointment.
The regulations do not discuss travelling to/from Tier 4 areas to fly from Heathrow, Luton or London City (which are in Tier 4) but this is presumably covered in the earlier legislation to which this is an amendment. Gatwick is not in Tier 4.