No problem. I have a similar size house to you. 3 bed, 1 bath.
I have a Worcester Bosch Greenstar 28HE in the loft feeding a DPS Pandora heat bank, also in the loft. No additional cold tanks at all. Hot water is mains pressure, with a flow rate of 40 litres per minute @ 60C.
Basically, both a system like this and a combi are going to provide absolutely superb showers, as they both provide mains pressure and the shower head or valve will limit flow rate to below the capacity of the boiler.
The main differences between the systems will be on bath filling performance or on having multiple showers. If you have/do neither regularly, then the combi will save you money.
Note that if you install in the loft, there may be additional costs, most of which didn't apply to me because they were already present.
1. Loft must be boarded. 2. Loft must have lighting. 3. Loft must have mounted loft ladder (can fold away). 4. Hatch must have guard rails. 5. You need a slightly more expensive vertical flue. 6. You need longer pipe and electrical control runs.