What are the ratings of each appliance? in KW?
You cannot take both off a 45amp switch,you need a separate one for each appliance .You wouldn't get the cables in anyway.6mm cable will carry approx 36 amps in total. so a 4kw oven for instance would draw 4000 Divided by the voltage(235) =17 amps...
Where did you get 1 bar from...................
Any New installation pipework is 0 mBar drop.
Existing installation is 4mBar drop With appliances connected with a U6 meter
8mBar drop with a E6 meter existing installation as long as there is no smell of gas.
Stick to 0mBar like i...
get it out and fit a Baxi 80 eco,they are £500 and should be able to get it fitted for £200-£250,The puma's and combi 80's are nowt but problems and you'll spend a fortune on it.I don't recomend anyone who is not competent and gas trained to even take the cover off any gas appliance.