UK of 1946 ISOT to 100 AD

  That is a huge problem as I doubt there's enough spare capacity in the European/Med world to meet Britain's needs, let alone the problems of shipping it to Britain.

  Fuel will also be a problem even if the North Sea oil and gas facilities and off-shore wind farms are brought along.  If their not we're in serious problems.

  True there is a lot of fat in terms of we can get by with a lot less than we consume nowadays but that's going to be an unpopular issues, especially given how weak the government is and even with WWII level rationing and seeking to regrow the fishing industry as fast as possible there is a probability of actual and possibly widespread starvation.

  Well we do have the advantage of having just gone through the war with strict rationing still ongoing - and actually getting tighter in many areas due to the economic pressures in peace-time - plus massive attempts at home production.  Albeit that without any colonies oil is going to be a serious problem which will affect fuel for agriculture and transportation as well as fertilizer production.  I still think that a lot of people will die however and possibly a desperate rapid colonization of Ireland and Gaul.

  Again with oil there are no local sources known at the time nor knowledge of how to find and exploit North Sea supplies even if it was known about.  You have Trinidad, Nigeria and then possibly parts of the Persian Gulf as the places you would have to reach and then build all the infrastructure including ports for shipping before you can supply amounts to Britain again.  I can see a lot of ships reverting to steam for quite a while along with much of the infrastructure in Britain.

  The Roman empire is going to be upset at losing its territory as, as well as Britain its likely to lose Gaul as well and possibly other places.  Also its so highly dependent on slavery that would be a big issue for both Britain being willing to help the empire and also for it to do any real technological development.  Plus by this time, while still in the Principate period its an empire so there may be little option for people to experiment without becoming unpopular with the powers that be. 

  How Britain and the Roman empire interact with the small numbers of down-time Christians and how much British Christianity will have in common with them will be interesting to say the least.

  One other issue will be what will groups like the Jews and Poles in Britain, along with American forces and German POWs will respond to the old world they find themselves in?  Its after the big Jews revolt that saw the Temple destroyed and many Jews dispersed from Palestine but after the holocaust so recent in memory would the Jews population in Britain seek to 'restore' a state in Palestine and if so how will they clash with the Romans and also interact with their own earlier versions.  Will Americans seek to 'reestablish' the US or the German POWs see any connection with the early Germanic tribes?

  Its true there's less open racism in the Roman empire than in Britain at this point but Britain does have a stronger rule of law in terms of human rights.  They would be appalled with things like the use of torture in Rome and the fact that Roman citizenship still applies to only a minority of the population of the empire.