I don't know if error code F1 means the condensate drain is frozen but sounds like it might be. It's a common problem with many makes of boiler but it can be avoided. For starters any section of the pipe outdoors should be of sufficient size and insulated. Many plumbers use too small a pipe which makes it prone to freezing.
Watch this video from another boiler manufacturer ...
http://www.worcester-bosch.co.uk/homeowner/customer-service/common-winter-boiler...Routing the pipe to a drain indoors is a good solution IF there is a drain handy. If there isn't then it's an expensive option. Other solutions such as enlarging the pipe, insulating it or perhaps installing a pipe heater might be easier.