Just make sure the chain is tight between the crank sprocket and the inlet cam sprocket when your timing marks are aligned at 10 and 2 o'clock. Then cable tie the chain to the cam sprockets to make things even easier. Slacken the camshaft bolts slightly so there not mega tight before you remove the tensioner, this way if you accidently turn the engine over slightly trying to lossen them you can just turn it over again until its all line'd up nicely with the chain tight between the inlet and the crank. Remove the tensioner and the cam shaft sprokets. You could bungee cord the sprockets up to the bonnet if you want to keep the chain tension round the bottom sprocket but its not essential, I'd just stick a couple of screwdrivers though them to stop them falling down.
When the cams come back, refit cams and the sprockets carefully without moving the crank, then turn the camshaft very slightly to ensure the tension is back on the front of the chain WITHOUT turning the crank (Its quite stiff so shouldnt move). Double check the timing of the camshaft sprockets are 10 and 2 o'clock again, then refit the tensioner, BUT you have to reset the tensioner first!! To do this you have to push the spring loaded part of the tensioner back into itself and turn it anticlockwise slightly so it stays in. Insert the tensioner with sprung loaded part vertially orientated and push hard so you can start the thread. As you turn it clockwise to screw it in and it pushes against the tensioner, the spring releases itself again and loads the chain up, at whish point it gets harder to screw the tensioner in. That sould be it. Take the plugs out and turn it over on a spanner a couple of times to check its all clear and you cant go wrong....well, you cant do any damage i dont think, lol.
