Do heater matrixes come with the valves etc?

Also, if I had a leak from there how would I tell? I found a puddle of water on the small ledge under the black thing after a longish run (and leaving it overnight). Also whilst driving it on a long run the coolant temp went below the lower mark when I drove at 30mph, but stuck just below half way at 70mph on the motorway. I can hear a little sound from the heater matrix, but this may well be the usual heating up/cooling down noises you get?!

I'm still getting the peculiar temperature drops at lower speed but cannot detect any leaks, no steaming windows.

Thanks in advance.

the heater matrix is basically a crude radiator, it doesn't need any valves on anything, if it was broken you would get steam coming through the air vents as you drive along the road

I wonder where my annoying temperature variation is from :S oh well. Have renewed thermostat and ran with cap off.

There is a temperature control valve on the inlet of the heater matrix. Its a doddle to change, and only a few quid.

Sorry I mean the temperature on the gauge of the car itself. Goes down if you drive at a slower speed. This is after renewing the thermostat, and flushing top radiator hose and engine block with a hose.

From searching around for info, I'm guessing it is a leak somewhere but it eludes me, or the heater matrix is a little blocked up. The other possibility is probably the head gasket but none of the usual signs.

I'll take out the heater matrix anyway and give it a look over and flush through as it's the only part of the cooling system I can't get a really good look at, and haven't flushed directly (even though I guess it should have got some flow from hose in thermostat housing.)