As you say, they are pretty much the same as now. The only difference was that they were smaller. Before the Ind. Rev. the majority of people worked the land in one way or another, so they were spread out in farms and rural communities. With the coming of the Ind. Rev. and things like cotton mills and foundries, people became more centralised into towns as they were all working in a concentrated place (ie a factory). As some factories used components from the next door factory, the phenomenen escalated until you got thousands of people living together, often in some squalor. Some factory owners tried to make a better life for their workers by building a complete new town for them (eg Saltaire, Bournville), but this of course was to their advantage as it guaranteed their workforce was on the doorstep.
My assumption was that the old major cities would either have been the important religous cities (Durham, Winchester, Canterbury, etc) which were left behind by the IR, the major trading ports (Southampton, Liverpool, etc) or strategic cities (Carlisle, Warwick, etc). I presumed that the likes of Birmingham, Sheffield, Coventry were fairly insignificant before the IR. Is this the case?
Well of course Coventry is also a cathedral city. It all depends what you mean by insignificant. Before the IR the economy was based on the production of foodstuffs. These had to be sold at market which was usually at the nearest big town or city. Of course, all food was sold locally as there was no efficient transport system to send it anywhere.Most towns had at least weekly markets and these were supplemented by annual fairs (eg Nottingham Goose fair). The other thing to realise is that the population of the whole country was much smaller and, on the whole, people didn't travel from where they were born. So even 'big' cities were not that big.
Norwich "grew in prosperity and population to become the second city of England by the early sixteenth century. It remained in a position of pre-eminence amongst English provincial towns until the industrial revolution." [Source: http://www.uea.ac.uk/menu/campus_and_region/about_ norwich.html
] No wonder the football team are doing do well ;-)