If you apply for patent protection in the UK you will not be protected anywhere else in country. Also if your application contains information about military technology, or could harm national security or public safety, you must request permission to apply for a patent abroad.
You can protect your invention in many international countries using the Patent Co-operation treaty ( PCT) through The World Intellectual Property Organisation (WIPO) Treaty. You can apply through the UK IPO, the European Patent Office (EPO) or WIPO.
A PCT application is initially processed as a single application when you will receive an international search report and written opinion. Your application is published around 18 months from the earliest priority date. Your application then has to be processed in every country separately.