Naval and Military Press has these current DVD-ROM bargains. I have a number of these myself - and rather wish I'd invested in the Military Operations, France & Belgium instead of filling up my bookshelves with red-spined volumes. You can buy the DVD of these volumes for £180. I think I was paying around £30 a time when I was buying these Battery Press / IWM imprints in the eighties and nineties. My incomplete set goes up to the end of 1917 and takes up eighteen inches of bookshelf. What's more, I need to refer to indexes to find what I need. Here on a single DVD-ROM, you have everything at your fingertips - and it's fully searchable. After 25th January, this will cost £45 more, so make the most of it now.
The other stand-out publication here is the War Diaries' DVD-ROM: 4,500 separate war diaries of battalions which fought on the Western Front, comprising 1.52m pages in full colour - £360 now or £450 after 25th January. I was looking at my copy this afternoon - so much easier to search than on Ancestry. Remember too, that Naval & Military Press offers an interest-free easy-payment scheme where you can spread payments across four or ten months. Well, why wouldn't you?
All of these DVD-ROM and CD-ROMs - not to mention the books from Naval & Military Press's extensive back-catalogue are offered with a 20% discount until 25th January 2016 - so you'll need to be quick to catch these deals.
Here's a list of the titles with links to each of them.