I've found a new writing hang-out: my local pub. It's a nice 15 minute stroll away to get me thinking about what I've got to do. It's cosy, with a lovely roaring log fire, nice coffee, lots of space, very quiet during the week, free wi-fi, friendly. I don't feel any pressure to buy drinks too often, although I'll probably stick to my 90 minute habit. I don't know why I didn't think of it before. The only problem is that it doesn't open until 11am and I imagine lunch time is a bit busier. Still, this is a success.
I love working in pubs. Just stick sternly to your 90-minute rule or you may be surprised by what you write.