Welcome Robert

There are much safer shrubs, and prettier that you could grow there. This holly, at the moment will probably not be causing any trouble, but if it is left, the potential for it to be a major problem is definitely very real.
This has a very strong and deep tap root, with smaller roots spreading outwards, which can in time take over a huge area, and will most certainly interfere with and destroy foundations , drains and pipework.
My suggestion would be to act now rather than later, before it gets too big. If you could top the tree (wearing good strong gloves) and first dispose of the top, and leave at least a couple of feet of trunk for leverage, dig a round trench approximately matching the width of where the top came to widthways, maybe you could dispose of the root by loosening the soil and using leverage to remove the root entirely. Don't attempt cutting level with the ground and leaving the root in, because this WILL grow back.
Better the graft now than leaving it.