Hello - I've been lurking here for a while, but since I'm in pretty much the same boat as you, I thought I'd add my say. Yesterday when I visited the doctor my BP, which has been about 120/70 all through pregnancy, was up to 137/80. Like yours, that's not worryingly high, but if it keeps going up...
I'm 36 weeks and also planning a HB here in England and the doctor mentioned that high blood pressure was one of the things that would make them advise me to come in to hospital instead. So I shall also be trying all the good suggestions here, and adding a few of my own. I have a vague memory of reading somewhere that music & singing were good for lowering BP (can't hurt!), and I know lavender oil is supposed to have a normalising effect i.e. it lowers BP when it's too high and raises it when it's too low. Massage is another good one if you can find a volunteer to give you one, or even try self-massage anywhere you can reach.
And if anyone can explain why protein helps I'd love to know! I think I get a pretty good diet, but fine-tuning it can't hurt either.
Sending you low-BP vibes!