That does seem a lot, I would class us as big spenders on food and we spend more like £350-£400 p/month on food for 2 adults excluding cleaning stuff and pet food, but including some alcohol. I guess it's a bit different in that I am mainly veggie (although DH is a big meat eater) so we will save compared to you, but the meat we do buy is organic and we mainly shop in Waitrose....
I guess the main question is does it bother you what you are spending, can you afford it? If you can easily afford it and are happy with what you eat then it doesn't really matter that you spend more than your friends. Food is both really important for health and also (IMO) for happiness so it makes sense to spend more in this area to me than on say clothes, or holidays (although of course we all make our own priorities).
If you did want to save money, I think I would advise the following (which all have environmental benefits as a side note):
-Reduce your meat consumption, especially red meat and expensive/prime cuts. Investigate using cheaper cuts of meat (if saving money isn't the prime consideration you could 'trade up' to cheaper cuts but higher welfare/organic meat), so perhaps stewing beef rather than steak, or brisket or a roasting joint rather than mince. Albeit Aldi is not the best for getting the less common cuts (I love Aldi in other ways, don't take this as an Aldi slag-off) - you might want to try an online butcher/meat delivery if you have freezer space to buy a big order? Try introducing veggie days, beans and pulses are dirt cheap sources of protein compared to meat, and much much better for the planet too.
-For fish, try and avoid premium over-fished or expensively farmed things like sea bass and tiger prawns, and go for lesser known/less popular fish such as coley, pollack, hake, basa. Again you might need to try a fishmonger or supermarket with a fish counter for some of this rather than Aldi. Frozen fish is also often cheaper than fresh and just as good...
-Reduce consumption of out of season and expensive fruits and vegetables, try and stick to in season British fruit in particular. Things like soft fruit, tropical fruit, out of season berries, avocados are quite resource intensive to grow/transport to the UK and cost accordingly. If you do get tired of apples and pears (in the winter especially) try buying canned, frozen or dried fruits rather than fresh.
-Buy in bulk where you can, reduces packaging and shipping costs and saves you money too. Aldi is not great here as usually you can only buy quite small packets, I buy things like pasta, rice, dried beans and pulses and some canned goods online.