Think very clearly, be alert at all times and do not leave any luggage unattended at any time in the airport / departure points. this will give you really a security problems and unnessary headaches.
Keep alert to any possible danger, do not take any unnecessary risks while in UK.
always better to Avoid places that are isolated, badly lit on the streets and stay away from crime hot spots where you can figure out.
Do not display valuables such as money, watches, jewellery, mobiles, and cameras.
Do not carry all your money in one wallet spilt the money so you are not stranded if you loose your wallet.
When purchasing any goods or services make sure you understand the correct price being charged and ensure you are using the correct exchange rate so you have a clear idea of how much it costs otherwise you can ask the sales rep until you fully understand.
Keep always a low profile and do not attract unnecessary attention that you are a tourist or business visitor.
Do not break local laws, rules and customs. These vary widely from country to country, some background reading and research can help stop misunderstandings.
Check if tap water is safe to drink, if not use bottled water, do not take ice in drinks, avoid non peel fruits and salads.
Eat sensibly and avoid any places where the food hygiene standard could be a problem.
Check for import regulations when purchasing goods in UK.