I'd heard how Denis had so many comics that some were even piled on top of the cooker and if you watch the film you'll see the evidence. I must admit my own house is getting pretty full of stuff (although I don't keep everything these days) but the kitchen is still comics-free so far!
Of course Denis put his collection to good use as it served as research for his numerous books on comics. The one shown in the news item is The Complete Catalogue of British Comics which I bought back then and has been invaluable in my own research.
The Catalogue featured nearly 100 pages of small cover images of comics from over the decades, plus a 112 page listing of almost every British comic title published up to that point. It provided dates of each comic's launch, key issues, final issues, mergers etc, plus notable artists involved. It also served as a price guide, although most of the prices soon became way out of date of course. (£20 - £50 for Beano No.1?!)
Sadly Denis passed away in the year 2000 but others such as Ray Moore, Steve Holland, Alan Clark, Derek Marsden, Mike Morely, Phil Clarke, Mike Higgs, Paul Gravett and more have continued to write about British comics history from the early days to the present. And long may such books continue!