That's one of the odder effects of a severe frost, Markafn. The top may get a little frosted, but cold air settles around the trunk and kills the bark. Most kinds of tree would be killed by that, since the growing layer under the bark would also be affected. Cordylines, however, like other monocots, have their growing cells and the cells that transport sugar to the roots scattered throughout the trunk, and the inner cells should be unaffected. Unfortunately, putting pruning sealer on was the wrong thing to do, since that will interfere with the trunk's oxygen uptake. Not much you can do about that now, and I hope it hasn't been sealed all the way around. Better to let the trunk form a natural callus to protect itself. If worse comes to worst, the new basal shoots will take over. Good luck!

Not much to add to Tug's comments above, with which I agree - if the main trunk dies back, cut it off at the base, but leave the new shoots intact.

The bark is still very loose at the bottom and I have pulled a little more off to allow air to the trunk and wiped some of the sealer off..did not realise that this was the wrong thing to do, thanks for the help .fingers crosses i have not damaged the trunk , the new shoots are growing well but realy dont want to loose the main trunk as have grown it from a small plant.

Here are a few new pic took tonight of the extend of the damage , any suggestions on how to help it would be appreciated

UPDATE

most of the bark has now fallen off , so there is space for the trunk to breath as there is no tree sealer on that part , also the crown parts that were damaged and brown have all dropped , but there is a middle stem which seems to have survived although growth is very slow , and still all the bottom leaves are turning brown fast.however the 2 new shoots at the base seem to be doing good, fingers crossed the whole tree will survive but it does look a sorry state.

Well at least it hasn't died completely. Thanks for the update.

The top seems to be opening very slow but there is no groth in height , and the brown leaves are cathing up with the top leaves, have cut the brown leaves off and now looks like just a trunk with a few tatty leaves on the top , i however have lots of new shoots at the bottom....this must mean the tree is still alive but still dont no wheather i should cut the main tree down , and if i do where should i cut it, i have heard of new shoots growing out of the trunk is the true ? would they out of mine , or should i wait a bit longer see if get any groth upwards from the top ?

I'd be inclined to cut it right down to the base and let the new baby ones take over if it looks that awful.

Have added couple new pics

Doesn't look great, does it? But then that's a subjective thing - it obviously hasn't died completely because there are still green leaves at the top, so its up to you what you do.

No it does not look great but i can live with that, would rather it survived tatty than died as will take a good few years to grow another one that tall...not sure if i am doing right here i am giving it a full 5 liter watering can full of water everyday ,is this the correct amount for a tree this size ? am i over or underwatering it ???

over, I'd say - won't need that much, more like a couple of gallons fortnightly in this hot dry spell. Water isn't its problem, its damage from the winter to the plant tissues.

Thanks bamboo for all your help..fingers crossed now

One more question , I have been up the ladder and looked in the top the growing point although is green has white sticky stuff in the crown of the plant and earwigs in it , would this suggest that it is dead or rotting ?

Ok all have given in , Think the winter got it to much , have cut it down , fingers crossed that the shoots will grow quick ,hopefully into a multi trunk tree...Thanks all for advice