if its efficency your after then a conventional tank and cylinder system with a condensing boiler would be more efficient than a combi.
however the installation costs may be a problem. if you have your exisiting system upgraded then by law when your new boiler is installed you also have to have a high heat recovery coil cylinder put in along with thermostatic radiator valves, room stat, cylinder stat and a programmer, your pipework between the boiler and cylinder also has to be lagged.
of course if you already have those fitted all you need is the new boiler.
if you opted for a combi then you would lose your airing cupboard although you could have a small radiator installed in the cupboard if you still wanted to air your clothes in it.