OK, postscript on the volume vs intensity debate. This is where you all get to shout, in unison, "we told you so!"
I've raced three times in the last seven days. I was going to experiment with, effectively, using the races to replace my interval sessions and putting in longish low-intensity rides on the intervening days. Already quite clear that I can't do it: or, at least, that I can do it but only at the cost of leaving myself absolutely on the floor tiredness-wise. Woke up this morning feeling fine, resting HR nice and low, but with my body telling me quite clearly that what it needed to do was remain in a supine position for as long as possible.
So, memo to self: think less, listen more, and confine experimenting to the less congested parts of the season...