Yes a combo could cope but if 2 showers are used at the same time the water flow rate would be poor. An unvented water cylinder is a better option.

Hi,
it depends on the flow rate you have coming into your house. Some large Combi boilers can produce 16L per minute hot water which is enough for 2 showers, however if you're not getting 16L per minute cold water into the boiler off the main it will only heat up what you give it. So if your only getting 9Lpm of cold water in it won't make any difference if you put a bigger Combi in, as you will still only get that amount of hot water.

In short you need to test your flow rate and pressure and make your decision from there.

Hi combi will do the job if your mains water flow is good enough you could use vaillant eco tec 838 plus, that boiler has hot water flow 15.9 litres per minute at 35degree. Regards Jozef Ilkowski

In most cases in the uk your incoming main is between 8 litres per minute up to around 13/14 lpm it’s quite rare to get 15/16/17 lpm really so I wouldn’t think even a large Combi would come into my recommendation to run 2 showers simultaneously , I would recommend a system boiler with an unvented cylinder