The zed will always lack punch when compared to those motors, but those motors are not direct comparisons are they? To compare you need to be thinking 2 seats for a start eg s2k, TT or a boxster. Those are the zeds competitors.
The interior is pretty poor on the earlier models but not that bad imo. Try getting in a MY06 car as the interior was upgraded significantly on these cars onwards.
Also, for less than £10k you can add some forced induction and achieve figures of over 400 bhp if thats what your looking for?
It really depends on what you want from your car really