If you remove the tree it may disturb the railings and leave the garden looking very open. This may be what you want. However, as the tree is growing quite high out of the ground, why not build a small brick/stone/wood (your choice) retaining wall around the tree about 75cms away from the trunks base. Trim down any grass and weeds and lay landscape fabric and then gravel or bark chips over the top. Don't bury the trunk at all but bring the 'ground ' up to become level with the base of the trunk. Does this make sense? You could even make the raised bed larger and it would become a real feature for the side of the garden. Small shrubs or hardy geraniums could then be planted through the fabric, which would suppress the weeds.

Clear all the weeds and put a couple of inches of top soil down followed by turf or lawn seed. keep it well watered until it takes hold. Don't forget that trees drain immense amounts of liquid from the ground!

I would use sand rather than soil, and just barely cover the topmost roots, before putting the turf on. I've learned the hard way that changing the grade around the base of the tree is a good way to kill it!

Are you in a conservation area ? if you are and you want to cut the tree down you will have to ask the councils permission

I dont actually want to chop the tree down at all. Just tidy up the 'lump' it sits on.
If I am to Lay seed, say this weekend (its supposed to be 25 degrees!), should i water the area daily? or would laying turf be better for this time of year? Also some sites have said that once cleared, I should put down weed killer and check that no more weeds come though before laying/growing grass.

Thanks for the advice all!

If you want an instant lawn then use turf but seed will be incredibly cheaper and both will need plenty of water (after the sun has left that area!) Using weed killer will delay you doing anything for 6 to 8 weeks!

Ok, Is there anything i need to pay attention to when laying turf around the tree root? I dont want it to look too 'artificial' as this isnt a flat, square lawn. As you can see from the photo of my neighbours tree/mound, the grass interacts with the tree naturally. Can this only be acheived with lawn seed?

Ok, I have half cleared the weeds/vines/old plats etc from the area. As there are a few i may have missed, and just chopped their heads off, Im thinking i should put down weed killer, to completely clean it up, before laying grass. Is there any weedkiller that is best for this, also do i need to worry about killing the tree?

Use a weedkiller that contains glyphosate. This will kill any plant that it touches by going into the leaves, so only apply it to the plants that you want to kill. It doesn't remain in the soil to harm other plants and shouldn't hurt the tree. but if you have cleared all the perennial weeds there is no point doing this. Any weedkiller that would clear weeds left underground will harm the tree. Better to spot treat any that come back up again later.