Morris Minor Owners Club

I have just removed the radiator from my moggie and given it the big flush and clean ready for a paint up, and thought I would also flush through the upper hose into the engine block to clean this out too. I only got a steady trickle out of the bottom pipe and quite a bit of squirt back from the top. Is the thermostat impeding the flow? I can't remember now if I should get a big gush out or not at the opposite end. (the thermostat is only 6 months old).

Yes it will be the closed thermostat restricting the flow. It will have to be removed, but if the housing hasn't been removed for some time and if it's not non ferrous alloy it may turn into a "wide screen epic" due to corrosion. Can be a pig to remove sometimes. I usually smear the fixing studs liberally with grease befor refitting which makes life much easier next time.
One important bit that is sometimes omitted is the removal of the block drain plug/tap, 1/4" or 3/8" BSP I think. Fitted in the top of the block rear right hand side looking from the front of the car. There can usually be an accumulation of sludge/scale trapped behind this. Try flushing with it removed and poking around with strong wire through the hole .

You may be interested to know that I have just bought a
BRASS thermostat housing? In other words no corrosion and
it won't break when it is removed unlike the alloy ones. It cost
less than £1 more than the aluminium job.

Where from??

It came from 'Minor Developments' (01562 747718) and cost
£8-95 plus postage. It weighs a ton!! I love brass- when I was a
diver i've inspected wrecks which have been under the sea for
nearly a hundred years and the brass was as good as the day
it went under.

Successful engine flush carried out after removing thermostat. I also located the brass plug in the spot pointed out. It was bunged up with sludge etc so poked the wire around as suggested and got rid of what I could. When I flushed though, no water came out of this hole, only the lower pipe. Should it have come out of here?

In an ideal world, yes there should be a flow of water from the block drain plug.
I had a similar thing some time ago but the concensus of opinion on the forum was that it wasn't too serious only if the remainder of the block is o.k. but I used kettle descaler as suggested by Willie and it worked in my case.
Next time the cylinder cover is off it would be worth having a go at clearing the accumulated rubbish by poking through from the cooling water holes on the top of the block with the plug removed.