Mike,
I've just recently block mounted on 10mm MDF a selection of my best
stuff for an early family Xmas we held last weekend.
I was shortly going to do a DIY explanation thread of how I went with
it to show the pitfalls etc that I learned.
As the weekend is now out of the way and the relatives all have
their gifts I can put it up on here (didn't want to earlier for fear
of them seeing their pressies online

)
I went the DIY path because I thought the price OW were asking
for A0/A1 was a bit on the steep side...and my prints weren't all
that good to warrant the expense
PS: prints done by OW btw. Prints submitted in morning, most were available
that afternoon except one which we picked up from another branch the next
day (they had run out of certain paper apparently).
Colour stuff was awesome, BW stuff was ok.
I would recommend asking for a small sample pic if the picture has
astro stuff. My terrestrial stuff came out pretty much as it looked on
our good LED monitor but the first print run of astro stuff was very dark.
Titles of moon images for example were almost unreadable.
With some adjustment at OW (by them) the 2nd print run was OK, not perfect
but OK.
Can't show you any pics as they aren't on my work puter. As soon as I get
home I'll email them/ write a quick thread to show you how they turned out.
Steve