Here's a piece from their Website:-
I am outside of the UK and Isle of Man and I want to play National Lottery games online and by text — what should I do?
If you are not physically in the UK or Isle of Man, or in a country where it is not lawful to play the UK National Lottery, you should not continue.
To play UK National Lottery games online and by text, you must be a resident of the UK or Isle of Man at all times, and you must also only play in a country where it is lawful to do so. This is because, in many countries, local laws prevent the sale or purchase of tickets for any overseas lottery, including the UK National Lottery, which is not authorised there.
If you do not meet these requirements, any ticket purchases you make may be declared invalid and no prizes paid, and we will have the right to reclaim any prizes already paid under these circumstances.
If you simply want to check your Account and not purchase tickets, please select the 'Accept' button to continue.
To ensure all of our players are treated fairly and consistently, the playing of UK National Lottery games in any country where it is unlawful to do so is prohibited under our Games Rules and Terms and Conditions. You agree to these when you register to play the UK National Lottery online and by text.
If you are travelling for a short period, you can buy your tickets in advance — for up to eight weeks for Lotto, four weeks for EuroMillions and one week for Daily Play. Alternatively, you may wish to play National Lottery games by Direct Debit. Please note that you must only set up the Account when you are physically located in the UK or Isle of Man and must not buy additional tickets or change your regular numbers while you are in a country where the playing of an overseas lottery is not authorised. If you need any assistance in setting this up, please refer to our Direct Debit Information."