If the steepish price has so far put you off buying The History of Christmas and Time Signature, the Short Trips volumes containing my two licensed Doctor Who short stories, you may be interested to know that they and the other 26 volumes in the series are currently half price at the Big Finish website. This means each hardback costs £7.50 -- a moderate price for a paperback these days -- or you can have both for the price of one a couple of days ago. Postage and packing are free within the UK, as well.
This is effectively a closing-down sale for the range, and stocks of some titles are supposedly low, though I have no information as to whether these two are among them.
Still -- if you've ever wanted to see the eighth Doctor celebrating midwinter on a brown dwarf planet, or the first Doctor exploring a world from which time is literally running out, this would be the opportunity. Other titles in the range I'd highly recommend would be Transmissions and 2040.