Engine oil

Guys I have been trying to do some maintenance on my recently purchased Disco 2 to save a few quid.
I have changed all the pads and disks and am now moving on to replacing the oils and filters.
I have run into a problem trying to remove the engine sump bolt - it's bloody solid and me swinging on it is slowly starting to round the bolt off.
Any suggestions will be greatly welcomed
Thank you.

Without trying to sound patronising are you sure you are turning it the correct way (sometimes if you are lying on the ground in odd positions/angles the natural tendency can be to turn the bolt in the wrong direction). Make sure you a six point (hexagonal) socket rather than a 12 point 'Bi-hex', a lot less chance of rounding the bolt head.