A big thanks to all who assisted me.
This afternoon I (feeling quite frustrated and a little deflated by the situation) visited homebase and bought
1 x All Purpose Hosepipe Connector
(Warning, these are a pain to deal with, because the tap isnt a standard type you have to have the right washer and the right degree of tightness - oh and it helps to open up the hosepipe to prevent a build up of pressure)
1 x Short Pan Connector
1 x Long Pan Connector
(whichever of these 2 isnt going to fit goes back to homebase)
1 x Replacement Valve Unit
Got home, first task was to get the Toilet (which decides to run without warning, and with a blocked pipe this could be disastrous) sorted with a new Valve Unit.
Turned the water off
Took the old one Valve Unit off, replaced it with this new one and secured it in place
Turned the water on
!!! NIGHTMARE !! the pan was filling up, the cistern wasnt filling up
Turned the water off!
After much fiddling and scooping of water from the Pan I thought it is probably that the flush is part way through a cycle and may need some patience.
Turned the water on
Just like I thought it started working after a little patience (and frantic scooping) it stopped filling the cistern.
Phew!
Next task - Thawing the soil pipe.
I took the advise of what others were saying and started at the bottom.
(For those who have this problem, it is hard to figure out what a cast iron pipe with water/ice or empty sounds like - FYI: An empty/hollow pipe sounds plinky or tinny, whereas a full pipe (with ice) just sounds thuddy)
It took a while of hot water spraying for the bottom part of the soil pipe to start sounding hollow, so I went to the next section, and after a bit more time that was sounding hollow
(this takes about 5-10 minutes)
I then started focusing on the junction point and the soil pipe exit from the toilet, this seemed to stay FULL (a quick tap with a broom showed me it was NOT hollow)
I kept at this for 10-15 minutes before thinking it might be worth a plunge!
I went inside, got my mop+carrier bag plunger and did a couple of plunges, a donk sound came from outside and I was hopeful that the blockage had passed... I poured a little water down the pan and it disappeared (such a wonderful sight!) I followed this up with some hot water (even hot water with salt mixed in towards the end) and it was going down... JOY!!!
I am unsure if my plunge dislodged some already part melted ice (from my outside hosing) or if there was a thick blockage of ice in there and since there was emptiness on the other side of the blockage, newton kicks in and the pressure from the plunging kicked it into touch.
I of course need to replace the cuff so that we avoid any leaking from it in the near future, however I am now the proud owner of a working toilet.
It is only when you lose something so vital that you realize Humans and Animals are just a few technical advances apart!
Thank you
Thank you to all who offered their advise. I hope my trials and tribulations have amused or enlightened any others with the same problem and all I can say is as follows
1 : In such cold weather put a hot salty bucket of water down every sink hole you can in the morning and evening
2 : If you have a blockage in your toilet and a quick 1 or 2 plunge doesnt fix it and the weather is very cold, you could have a frozen soil pipe, whack it a little with a stick and see if it makes a hollow or thudding sound... if its a thud you may have ice, stop plunging and get thawing
3 : If you have a broken toilet part that is working but not working well, fix it or replace it. I thought a simple overflowing toilet cistern was nothing to worry about until I now think that the constant draining may have caused ice to build up in my soilpipe and has cost me more in stress and time that just replacing the part! it isnt worth being tight when it comes to your plumbing!
4 : My external soil pipe can be thawed with a hosepipe and hot water and should this occur again I know that this simple step is all it takes
5 : If you are plunging or dealing with any type of toilet blockage, cover your floor with towels. No matter how it happens, your toilet will overflow or spit dirty toilet water at you and it will get into your carpet / floor and stink
6 : Ask for help in this forum, there are some friendly and knowledgeable people here, if i ever get stuck again I know where I will come to!
Good luck to anyone with a similar problem