Places like Harvester tend to have adequate salads. You don't have to go anywhere near any raw vegetation. But aside from that, pet food us still pet food, nice doesn't come into it.
Wholegrains are a good base ingredient on which to base a salad. You could add kidney or endamame beans, nuts and seeds and / or golden sultanas, raw veg or roasted veg such as beets and aubergines, goats cheese and griddled peaches / figs, or pear, stilton and walnuts, and always drizzle with copious amounts of balsamic glaze. Don't forget plenty of seasoning and dressing and fresh herbs such as mint and dill.
I should add that cooked, mixed wholegrains (wild rice, quinoa, puy lentils, spelt, wheatberries and suchlike) are readily available to buy in all supermarkets.
I find Tescos own just as good as any. You can add cous cous to fluff it out a bit.