Does this just pull out from under the boiler?

[Radian]

I want to add a cable to the  Electrical Cartridge in my Glowworm Flexicom boiler. I think the idea is that the cartridge is removable without having to open the boiler case so sparks can do their bit without compromising room sealed units. The instructions say to push the cartridge into the housing on completion of wiring:

 

The trouble is, I've undone the fixing screws but I can't seem to pull the cartridge out. I'm not sure how much force it should take so I thought I'd ask if anyone knows for sure that it should just pull out?

[ProDave]

Can you post a very close up picture of your actual cartridge on your boiler.  I bet there is some form of catch that it clicks into first before you put the screws in.

[TonyT]

2 screws to take the cartridge off the main board I think