In the UK there are mostly 3-5 Marks on silver, not necessarily oriented or aligned the same. Marks include maker's mark, Town mark, Standard (Purity) mark, Date Letter, and Duty mark.
Without seeing the marks (you can send in a photo of the marks in a follow-up submission if you like) it is next to impossible to determine the date, (this will appear as a letter) because the shape of the letter and the shape it is in are both just as important as the letter itself.
The same applies to the maker's mark which would be the FP in a circle. There are a number of UK jewelry maker's initials - FP.
What we can tell you, is that the anchor is the town mark for Birmingham and the left facing lion is the standard mark denoting sterling silver.
About the thistle on watch-face. Did your Dad have any family connections, with Scotland? The emblem of a thistle is a symbol for Scotland. Is is the national emblem of Scotland, which you probably already know as you are from the UK.
It is said, that a thistle saved an entire Scottish army. A thousand years ago, during the Vikings invasion of Scotland, an advancing enemy warrior stepped on a thistle and cried out in pain with the consequence of waking the sleeping Scotsmen. In gratitude, the Scottish King Kenneth III adopted the thistle as his nation's emblem.
