I guess that's the problem – the traditional British meal always has meat as its centrepiece. Simply making that centrepiece smaller is likely just to make it disappointing. My parents won't ever eat a meal without meat (not an issue, since they have a freezer full of dubiously sourced meat, another story...)
It doesn't have to be complicated. I made broccoli cheese yesterday for my supper. Took about ten minutes – floret the broccoli, steam it till tender while making a quick cheese sauce (knob of butter, a spoon of flour, add milk till of the correct consistency, then grated cheese). Mix up, two minutes under the grill with a bit of cheese and a sprinkle of breadcrumbs on top. Et voilà. Many pasta dishes don't require or benefit from the addition of meat – there's plenty of scope for veggie curries, falafel and the like. Generally, I'm not big on pretend meat, but I really like the Cauldron sausages – I'm not entirely sure they taste like sausages but they're tasty nevertheless.
My exceptions are veggie chilli and bolognese – sorry, I've tried to make them work and failed, they just seem to need meat.