I really don't think there is much good that can come from lowering your rates.
From a client's point of view, they're going to see that you've lowered your rates and then you've immediately sent their alarm bells ringing as to why they might have been lowered.
They'll probably assume you're not getting bookings in, then they'll wonder why you're not getting bookings in, is it cause your service isn't good enough or you don't look like your photos? Or do you personally not think you're actually worth your rate? etc etc. Then there's the desperation factor that VG mentioned above. You're just opening yourself up to hagglers and idiots as they know your rate can be negotiated and/or they think you're desperate. I think it's important to remember that these people are considering more than just your rate when booking.
Has anyone here ever tried increasing their rates when it's quiet?
A while back I'd been working for a good year or so before I was able to offer regular incalls, then after 7-8 months of regular incalls I started to go quiet over a few weeks, like I'd lost the new girl factor. Not dead, but notably quieter. So I put some new photos up and put my HH and hourly rate up by £10 each. Very quickly my phone was ringing off the hook and it stayed like that for ages. I did better than I had in months. There weren't any reviews go up around that time either that I was aware of that would have contributed to it and I don't think it was a coincidence either.
If you aren't getting bookings in at say eg £110ph, it won't make any difference if you don't get bookings in at £120ph, so maybe it's worth a try? It sends out a better message than lowering them!