Sewing machines are like most other things, you get what you pay for. It's not just the range of fancy stitches etc, it's the robustness of the thing and the power of the motor which increases as you go further up the price range.
If you are determined not to buy second-hand then you've got to be looking at £100+ for something that won't splutter and die as soon as you ask it to sew more than two layers of lightweight fabric.
Given the current discount the Hello Kitty machine (already suggested by someone) on the
Sewing Machines Direct website is probably the best buy. If not the Brother LX17 next to it is probably the nearest to what you are looking for. It's got the simplicity of a drop-in bobbin and it's by the same manufacturer (but probably out of a different fctory!) to your main machine.
If I was wanting a machine for taking out once a month to a P&Q group I'd take the vintage Featherweight
but you'd be very lucky to find one of those for less than £100 now, they seem to go for about twice that and are restricted to straight stitch, the 222s with zig-zag are usually more like £400.