Your local Evans / Cyclesurgery would be a better place to ask this question
Or bike radar commuting section.
Assuming you don't go off-road, you don't need a mtb, the bigger wheels of a hybrid will be better suited. You do not need any suspension either. Something like this:
but there are literally hundreds that would cover you needs from Evans alone.
As far as the balance thing goes - it shouldn't be any different from bike to bike really - probably more pschological. But getting a road bike will be lighter - so faster and easier (a bit), and you don't have to have drops and can put on wider, more comfortable tyres, which should help you feel more confident.
Or bike radar commuting section.
Assuming you don't go off-road, you don't need a mtb, the bigger wheels of a hybrid will be better suited. You do not need any suspension either. Something like this:
but there are literally hundreds that would cover you needs from Evans alone.
As far as the balance thing goes - it shouldn't be any different from bike to bike really - probably more pschological. But getting a road bike will be lighter - so faster and easier (a bit), and you don't have to have drops and can put on wider, more comfortable tyres, which should help you feel more confident.