Stevie, we're all learning as we go to some extent, but one of the massive keys is never increasing both mileage and quality.
Therefore, you've done right only increasing the mileage. If you wanted to keep that level of mileage, you'd want to bed it in for a while, and then add the second hard session.
If you really wanted a true base phase, you'd keep your mileage high, intensity low in training and not racing, and stay like that for a couple of months. Can you not race for that long? 
Not 100% sure about XC racing fitting in. On the one hand, it's less smashing than the road, but I guess on the downside, if you're doing that on a sunday, the long run gets binned, which is a key part of the base build up.
Also you'd need to bin off the usual taper before, then recovery after, as the whole point is keeping the mileage up.
Edited: 28/09/2012 at 20:20