We don't have an Aldi yet, but do really love Lidl: wonderful fruit and veg, "aged" beef for roasting as good as the more expensive stores and meat in general is good and inexpensive, variety of hams, tortillas, instant coffee and breakfast cereals. Their jams are particularly good. Of course you can't get everything and branded goods are at least as expensive as the other supermarkets.
My husband loves the centre aisles too, we've had some real bargains such as fancy weighing scales (for people, not baking) for <£15 and virtually identical to John Lewis for >£50.
You do have to chose the time of your visit with care, but as we are retired we can go midweek. We went past a Lidl in Sevenoaks the other day and saw that the car park was full of new BMW's, Mercedes and four wheel drives...