[Alec Dawe]

To get a container under the rad you have to take the bottom shield off underneath, can't remember how many bolts, but one thing to remember is the plastic shield tends to age harden, and a few big 'penny' washers are a good stand-by in case any of the bolt holes crack too much.
I think there should be a drain **** on the right hand side of the block, towards the back, but how turnable this is I wouldn't like to guess, and you still need to get a container under.
You can use 'G' clamps on the hoses either side of the heater matrix, so you would only have to contend with the water in the matrix itself. I don't know how much that would be, but I would think not more than a pint and a half.