2008 17" MacBook Pro current leak

Question

I'm using the above computer, and it still works reasonably well. There is one huge issue though - there seems to be some sort of current leak that prevents the trackpad from functioning correctly. To make it work properly, I have to 'ground' the chassis with one hand. When it's really bad, the whole computer 'hums' with current. Over time, the current seems to increase, leading to very little 'shocks' which feel like the hairs on my forearm are being pulled. It can be discharged by touching a conductive item, like my iPhone(!) or the radiator, but that really isn't ideal. I've put stacks of research into this, so I can tell you that I'm using the grounded (3 pin Uk) adaptor, both directly into the wall socket and/or into surge protector mains adapters, and both with the long lead and the plug that fits onto the line-lump - neither make a difference. It happens when I'm barefooted, when I have my trainers on, on wooden floors and carpeted floors. I've even tried placing both hands on the computer and jumping into the air so that there is no ground. There is no longer a battery attached - after the 2nd one expanded I decided not to buy another. I've read that prolonged use could lead to long-term health risks, but I can't afford to replace the computer, and besides, I've read that the issue is also common on newer Macs. Is there anything that can be done? All my research up to this point suggests that there isn't, but I'm hoping there's a Super User with a solution. Thanks for looking.