I use them all the time for food - they're the cheapest to start with for Royal Canin Sensitivity Control, and if you type 'Chemist Direct Discount Voucher' into Google you can generally find a 5% or even 10% discount voucher code too, so a 15kg bag of food works out to be £10 or £15 cheaper from there than the cheapest other online store..
The last 3 times I've ordered bags of dog food from them I've received them the next day - and that's with free delivery due to the value of the order.
They don't tend to stock the biggest range of pharmaceutical dog products - eg they don't stock the Doxion tablets in the size I order - but no matter how much hunting around I do I always end up back there for the food.
And another plus point - Ordered a few other things a while ago and they didn't have an item in stock, and weren't likely to get it, so sent me an email to explain they'd cancelled this bit of the order, but despatched the rest so as not to hold it up, giving me the option to re-order the missing thing on the understanding it'd be a while before I received it.
Love places like this. Best prices combined with the best customer service. Can't beat it.
And no, I don't work for them, and am a real online shopping tart as I'll always go for the cheapest unless I've had a particularly bad experience with a shop.