Yes that system would fall under Building Regs BEST PRACTICE for central heating and hot water provision (subject to tests being carried out on the water supply for the unvented cylinder pressure and flow rate did they spend any time at your kitchen tap? if they did not then they did not do the tests)
Also insure that the installer is CORGI registered, holds the G3 certificate for the intsallation of Unvented Cylinders and, finally ensure that they will be informing the local authority that an unvented cylinder is being installed. Normally this is just a matter of dropping them a line but, depending on which authority, a charge may be incurred.
As for what manufacturer my recommendations (based on good quality stuff and excellent after sales service should a problem arise) are
Heat Rae Sadia MEGAFLOW cylinder (ten year warrantee) and an Ideal ICOS condensing boiler (new model is a HUGE improvement on the old and comes with a two year guarantee)
Costs
Icos (plumb Centre) $600 plus VAT
Megaflow 120 $ 500 Plus VAT
don't forget to conform to best practice the Building Regs State that the following should be installed/carried out
1 Thermostatic Radiator Valves on ALL radiators except one that is in the same room as the room thermostat.
2 Cylinder (Megaflow has an inbuilt one so a saving of a tenner to be made here) thermostats MUST be installed.
3 A programmable Room Thermostat with Anticipator MUST be fitted
4 if the property is of an area bigger than 150m2 then a second heating Zone valve MUST be fitted
5 A Full Programmer That allows the heating and Hot Water to be controlled and time separate MUST be fitted
If you want any further info for the Energy efficiency Building Regs (2002) just visit
www.boilers.org.uk
Hope this helps some Good Luck with it