I did this job this afternoon - pretty straightforward -
Malcolm's hammer on the spanner trick worked perfectly to undo the HP pump drive - no need to counter hold the camshaft or anything.
Unless you're confident with your technique though I would recommend removing the bearing cap first to get the seal out. I have the smaller seal picks and a selection of screwdrivers but I failed to pry the old seal out although I didn't try that hard as I was scared of scratches. On the TD I found it's better to remove the intercooler anyway for more space and once you've done that it's only 3 more bolts to get the valve cover off, not really anymore work.
Using the old seal, a deep 35mm socket and a soft face hammer it was easy to get the new seal installed square. I torqued the cap down before installing the seal.
I have the timing belt side to do next and I'm thinking of getting one of these sets:
http://www.ebay.co.uk/itm/Crank-Seal-Remover-Installer-Kit-Set-Oil-Seal-Crank-Seals-27-58mm-Universal-/251364417119?pt=UK_Hand_Tools_Equipment&hash=item3a867c9e5f
If it makes this job quicker, safer and more reliable it's probably worth it as I should probably do the seals on all our BX's