Mk1 Focus 1.6 Petrol - which heater pipe do you disconnect to refill coolant?

I'm due a coolant change on my 54 plate 1.6 petrol Focus. I've had a look in my Haynes manual and viewed a few online vids for some pointers in relation to refilling the coolant. The information I have states I need to disconnect the heater supply pipe to refill, then top up the expansion tank. Trouble is, I'm finding conflicting information on which pipe I need to disconnect.

When I look at the bulkhead from the engine bay, there are two pipes going through into the heater. One above the other. My Haynes manual states you need to disconnect the pipe that is attached to the engine under the ignition coil (the bit where the HT leads emerge from).

However, the Haynes youtube vid (link below) states you need to disconnect the top pipe at the bulkhead and refill through that pipe until coolant emerges (1:33 in the vid below):

https://youtu.be/MgioniPjnJo

Can anyone clarify which pipe I need to disconnect and pour the coolant into? The top one or bottom one at the bulkhead, or at the connection under the ignition coil? I have attached a still of the vid to help. The top pipe has a bit in the middle that I guess you can split and seems to come from the front of the engine from the thermostat. I'm guessing this is the supply pipe?

Many thanks in advance.

Oh yes, I'm getting more confident working on the car. I solved my battery issue (which I posted about on here last year - thanks for the help), managed to fit a new heater blower motor last week and am just about to undertake a full service of the car etc. Only thing I need to look at is the rust around the wheel arches. Oh yes, had a new exhaust fitted the other day as I didn't feel confident enough about being under the car for so long. I'm working on that though and have proper axle stands, some ramps etc.