Met office
UK Outlook for Monday 10 Dec 2018 to Wednesday 19 Dec 2018:
Next week starts generally settled, especially so in the west, whilst scattered showers are likely in the east where they could be wintry at times. From mid week onwards the weather pattern becomes slow moving, with easterly winds developing and bringing showers to many parts, these possibly wintry away from coastal areas. Overnight frosts and patchy freezing fog are also likely at times. Any wet and windy weather is likely to be confined to the west and northwest, although rain may affect the south at times, bringing with it a risk of hill snow. Temperatures generally rather cold or cold, perhaps milder at times in the west, as well as in any brief unsettled spells.
UK Outlook for Thursday 20 Dec 2018 to Thursday 3 Jan 2019:
This period is likely to start with a mixture of weather, with spells of settled, drier and colder conditions with overnight frost and fog, but also with a chance of occasional bouts of windy and showery weather bringing a risk of snow. By Christmas and through the last week of December there is a more general trend towards unsettled conditions returning, with western areas seeing spells of windy, wet and milder weather, with the best of any drier but colder weather the east and south. By the New Year there is very low confidence in the forecast, but there are signs that weather patterns may become slow moving again, possibly bringing a period of colder and at times more settled weather conditions.
https://www.metoffice.gov.uk/public/weather/forecast