I would be suspicious of the ingredients in any main that was only £4.50 and therefore wouldn't buy it.
I'd happily pay 7 or 8 quid for a decent chilli, lasagne or cannelloni though.
I also really like it when these dishes come with a little cherry tomato and a sprig of parsley or corriander. It costs almost nothing and really creates a good impression of someone who's proud of their offering.
I eat in France and Switzerland a lot and nearly everywhere does this.