Duty Free when flying within UK?

The list below outlines the regulations but as you are travelling internal you have no allowance.

Duty free allowances and information in the United Kingdom
Duty Free: Liquor, tobacco, perfume
Tax Free: everything else

If you are flying inside the EU there are no longer any restrictions on the amount you may bring in of any of the following Tax Free goods:

perfumes, cosmetics, skincare

electrical and photographic equipment

fashion and accessories

gifts, jewellery, souvenirs

When travelling to the UK from the EU
You do not have to pay duty on any items bought in another EU country as long as:

tax was paid at the time of purchase

the items are for your own use

they are brought into the UK by you

If you want to avoid drawing the attention of Her Majesty's Customs Officers don't arrive with a trolley of holdalls bulging with cartons of cigarettes and crates of vodka.

These limits apply when travelling from the following countries:
Czech Republic: 200 cigarettes, 250g tobacco, 50 cigars, 100 cigarillos
Estonia: 200 cigarettes, 250g tobacco
Hungary, Latvia, Lithuania, Poland, Slovakia, Slovenia: 200 cigarettes

Abolition of duty free goods within the EU
On 30 June 1999, the sale of duty-free tobacco and alcohol at airports and at sea was abolished in all 15 EU member states. Although there are now no limits imposed on importing tobacco and alcohol products from one EU country to another, travellers should note that they may be required to prove at customs that the goods purchased are for personal use only.

EU countries
Austria, Belgium, Cyprus (Greek part), Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Irish Republic, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Slovakia, Slovenia, Spain (but not the Canary Islands), Sweden and the United Kingdom (but not the Channel Islands).

When travelling from outside the EU
The following allowances apply when travelling into the UK from outside the European Union, as long as they are for personal use and are carried by you:

200 cigarettes; or 100 cigarillos; or 50 cigars; or 250 gms of tobacco

2 litres of still table wine

1 litre of spirits or strong liqueurs over 22% volume; or 2 litres of fortified wine, sparkling wine or other liqueurs

60cc/ml of perfume

250cc/ml of toilet water

other goods including souvenirs up to the value of Â£145

What you can't bring in!

firearms

illicit drugs

pornography