Most countries now require passports to be valid for at least 6 months after your return home. If your passport is in its final year, please check with the embassy of the country you're visiting. For further information, contact the Passport Office at 08705210410 or check the FCDO website. The section you need on the FCDO website about passport validity is 'entry requirements' Here is a quick link -  FCDO website

Please allow up to 10 weeks to apply for your passport, There are fast-track options available if you require your passport urgently. If you need support on how to apply for a UK passport please find some additional links below:

HM Passport Office - Passport services

How to apply - Apply online for a UK passport 

How much it costs -  Passport fees