Toilet not flushing but not clogged

[spanner]

You'd need an air test kit
Is the soil pipe made of plastic or cast??

 

[spanner]

You're not a plumber.
To explain isn't going to assist the issue.
The best thing is to get a plumber in to check things out for you.
Carrying out the air test would mean plugging the soil pipe from an access to check there's no build up of pressure from the ground floor to the top of the SVP where it's aired to atmosphere.
If there was a build up of pressure !
This means it's blocked and not being vented to atmosphere properly.
Don't lets get complicated.
As surely it's something more simpler..

 

[JusKel]

It sounds like vent or soil pipe under ground is blocked as mentioned above.
Can you cut the old pipe/vent to check ?
Other option could be to change the multiwick for type with vent/durko built-in

 

[spanner]

Well I wouldn't try to rod it from up there to see whether there's an obstruction caused from Where the upstairs loo were removed.
Is the soil stack made from cast iron??

 

[SB101]

Well I wouldn't try to rod it from up there to see whether there's an obstruction caused from Where the upstairs loo were removed.
Is the soil stack made from cast iron??

Yes it's cast iron .

OK I think I follow the air test process too so will try sort that tomorrow, weather permitting lol

 

[spanner]

Ok.

 

[heliotrope]

Anyone think it may be a siphonic pan playing up?

 

[JusKel]

If it's Cast iron then it's almost certainly blocked/obstructed (like arteries of the heart leading to a heart attack or full bowl in your case) with just enough space remaining for a slow trickle or hose to empty tru.
As the vent section is no longer used its clogging itself up deteriorating.

 

[Welder]

Anyone think it may be a siphonic pan playing up?

Now you mention it Ive seen many replaced with normal syphons. some work aftervavfashion but many don't...

 

[justlead1]

As Heliotrope has asked siphonic pan is a must to check it fits in with the dates.