If the tree is 10 feet high then the roots are normally 10-20 foot in depth and 6-12 feet is spread by now in loam soil. If clay then normally smaller. They tend not to be a problem with subsidence though, unlike willow and the like.

They do get large...there is a Monkey Puzzle in the the park near my house that is easily 20-30ft high. So you have to ask yourself if you want such a tall tree in your garden? I do like them and they are pleasing to look at but might be a millstone in 10 years.

Thank you very much for replying with your answer. That has really helped me in deciding what to do next. I would like to keep it but I think we'd have to move it and I have heard they are not easily moved and kept alive. I am wondering if I can get someone who would like it to dig it up and relocate it to their premises. Thanks again

I think 7 years in the ground will mean that the root system is quite developed. Certainly sounds happy where it is with the growth you mention; as they tend to be quite slow growing at first. What you could do is take a pic then post it here and ask if people think it can be pruned. It depends on how it is growing - with a crown or not. Some Monkey Puzzles trees can look fine being pruned, but most will not look good TBH after pruning. Selling or offering it is a way of solving the problem!

Agree with everything Kildermorie says - it has to be said though that I've seen monkey puzzles growing in front gardens in London which are no more than 8 x 8 feet, the garden I mean, not the tree. People usually remove the lower branches as they get taller, though I'm not certain how wise a practice it is to keep such a large tree in such a small space.
Oddly enough, this is one evergreen which copes perfectly well with being coppiced - that, though, rather defeats the object of having one, which is its stately, shapely, evenly spaced and tiered, interesting leaf/branch formation. Perhaps they should best be viewed as a temporary inhabitant in smaller gardens.

Thank you so much Kildermorie and Bamboo for your advice. I am so sad to think I will have to remove the tree it is a beautiful specimen. I have seen how people have pruned the lower branches. It has plenty of room really to grow, I just wish I hadn't placed it in the middle of the front garden but towards the end, but I never thought it would grow so quick. I will take a picture and post on here. It is absolutely perfect, as you will see. It is always admired by people and I rarely give my house number to any visitors that haven't been to my house, I just say look for the Monkey Puzzle tree and you're there! Thanks again.