I have been to both Ottolenghi restaurants in Islington and NOPI in Soho. I really wanted to love them as much as I love the cookbooks but, sadly, that was not to be. My view on both restaurants was pretty similar so I'll review them in the same post.
Both restaurants had much more limited vegetarian options than you would expect from Ottolenghi's Guardian column and cookbooks – it's not so much that there weren't quite a number of options as that they were almost uniformly “lighter” options, more accents to the meat dishes in the mezze than substantial in and of themselves and, often, with ingredients repeated throughout the vegetarian options so it was hard to get dishes that were genuinely different from one another.
Essentially, I got the impression that no-one had actually looked at the whole of the menu from a vegetarian's perspective – each individual dish was nice but it was hard to put together a complete meal from the vegetarian dishes on the table without a) repeating ingredients a lot and b) eating a lot of vegetables and not much protein/carbohydrate. I don't want to sound like a barbarian but, really, I do expect to be full after spending £30+ on food in a restaurant. Even by the standards of nice London restaurants, I thought both were overpriced – it's not that the food wasn't good but it just wasn't quite priced right for me, for the prices they charge, I expect (literally) more.
I had one Islington restaurant specific gripe, too: we'd booked in advance but were sat on the long communal table without being warned of this on the phone – if we had been told, we would have changed the booking for a time when we could get a table to ourselves – the staff's attitude seemed to be very much “if you're in the know, then you'll get your own table, otherwise, we won't tell you”. I don't like that attitude much.
Overall, I'd rather stay at home with my cookbooks. Where I can get a table to myself.