I often say "Fill your boots". I do tend to swear a lot mostly Bloody hell and maybe the f word.
Coming from London, and now living in the USA, I have a lot of expressions I constantly use. I suppose the most common one is "bloody" as in "bloody hell" "Bloody Nora" though I wonder who Nora was! Then there are they usual others such as "don't get your knickers in a twist", "Daft Twit/Bugger", "stupid sod" , "sod it" etc. (unlike the Americans who say the word "stupid" as if it was spelled stoopid!
Since finding out what "Blimey" means, decades ago, I've long weaned myself off that one.
There are many more that I can't really come up with right now, I have to be in the position of having to say them to remember.
One of my American friends now constantly says the word "bloody" and it makes me laugh hearing her say it.
When I went to America many were confused when I asked them "Let's have Italian for tea tonight, yeah?" They looked at me dumbfounded until I realised they say 'dinner' instead!