I'd be really grateful for advice here. I have a Worcester Greenstar 42cdi that is just over 2 years old - Pressure is okay, pipe outside is lagged and covered. The water heating side is working okay. The central heating does not seem to come on as usual in the mornings. If I turn off and turn on again - then wait about 2 mins - I can use the controls to turn the heating to 'on', which works for about 20 mins then stops. Then I do it again and it will work fine all day but the display is showing a symbol that alternates between the symbol and the current temp. This is not in the book and when I google I can't find it. Error as follows: -| |- The following morning we have to do the same again. 3 mornings in a row we have woken up to 16 degrees! I think its related to the cold because it started when the weather got cold. In fact I used a kettle to ensure the pipe outside was not iced up as this happened last Winter and this is how I first got it to start (on the coldest day), but since then I havent had to do this to get it started. The pressure is about 0.5 when completely switched off but it is about 1.8-2.0 when switched on and running normally. Is there anything I can do or do I need to call a plumber out?