Afraid I can't help you much here mate. Can only offer that many times folks change glow plugs before they actually need to. If you're having problems starting your B, then ok. Just make sure it's the glow plugs and not the plug wires or something else. It does not typically get THAT cold in GB, but I'm not sure where you're at either as I realize it does get somewhat colder in the Northern parts. Just hate to see you go through the expense of changing plugs if it's not necessary.