though i dont own an F at the moment! most modern engines are 8 to 10,000 miles for minor service (12 months) and 20 - 22,000 miles for major (24 months) with maybe the the 6 month oil service in between depending on how hard the car is driven. lexus do the essential care service for vehicles which are out of warranty i.e. cars over 3 - 5 years old and although the ISF is not listed should be any more than £190 for minor and £390 for major but worth giving them a ring for a quote. or alternatively use one of the Lexus independent garages like Toyotec/ Jem Lexus or ABM if you just need a quick oil filter change. but they all based in/near London
http://www.lexus.co.uk/owners/lexuscare/service-your-lexus/essential-care-service-plans.aspx