We did our own - if you go on the passport service web site there are very specific head sizing quidelines. We just took one of our own and then sat there with a ruler, trying different sized prints until we got one where the head was the right size! It worked anyway.
Yes, the baby mustn't be smiling, wearing dark glasses or too much make-up, and be looking directly at the camera. Must have seemed like a good idea at the time. I wonder what the civil servant who proposed the idea is doing now?
It isn't SE1 but it's easy to get to on the Jubilee Line ... there's a photo shop opposite Selfridges on Oxford St (admittedly up several flights of stairs, so buggies are out and slings are in): they take fantastic photos and know all the sizes/rules etc etc (and it's worth going just for all the passport photos displayed on the walls)
The chemist on Borough High Street opposite the entrance the Borough Market (sorry can't remember name) does baby passport photos. They use a cushion so that you lie the baby down and they shoot from above. I was very happy with them when I used them earlier in the year.
Oh, sorry Jackie, I thought you knew (thought you'd commented on it in another thread).
Baby girl. 8 weeks old. No discernible interest in drinking cider yet, but she has been to two cider pressings, and spent a day picking apples (although, to be honest, she didn't really pull her weight).
Named after a jockey, and she's off on her second visit to (the races at) Cheltenham in 3 weeks' time to see her namesake win the Glenfarclas.
And the pharmacy on BHS does great baby p'port pics, so thanks again for the recommendation Catherine. (I think it may be called City Pharmacy?)