When to pick pumpkin

I have a pumpkin (I think) growing in my garden. It grew from compost from my wormery so that is why I think it is a pumkin. It is 8 inches stalk to tip and 10 inches diameter. It is orange where it is resting on the lawn and dark green on top - now flecked with orange. Many of the leaves have died back but there are still some leaves at end of (long) plant - it grew up into blackcurrant bushes as I didn't know when I was supposed to pinch tip out

Should I bring it in, protect it from frost or just leave it for now - we want to use it for a Halloween lantern with carved out flesh going into a pumpkin pie recipe I use every year.

 

Thanks for the info - I have been watching frost forecast and am leaving it for now - by weekend it will be more orange than green and I will prob bring it in - most leaves have died off now anyway