There is a Jessops store right next to my office and I pop in there quite a bit. From what I've seen, there are two types of people who come there (could be a common trend in every other store).
1) a person who wants to get a look and feel of all D-SLR's before he commits. Once he is convinced, he is going to do his own research and buy elsewhere, never in Jessops, cos it's outrageously expensive, be it any brand.
2) there is an user who wants a camera, thinks 'DSLR is the best', wants one today, right now and walks in to a store with commitment to buy. Asks the sales person, who shows him couple, but recommends one. Customer pays and buys the SLR. (I've seen this happen twice, and Jessops sold him C***n 450D). I reckon this is where their SLR business lies.
I'm not sure the reason behind they dropping Pentax, but I for sure will call them several times and enquire if they have Pentax in stock..
Regarding Jessops as a business, as Delgado said I remember they closed several stores in 2007.
As far as Pentax retailer in UK goes, there is no shortage of options if you wish to buy one, so Jessops not stickong pentax is not such a big deal. But having them in stock, couple of posters stuck outside, and salesperson pushing the brand might've helped with some sales on second type of buyers i mentioned above.
I walked into Jessops two weeks ago and asked for an Ilford HP5 roll and he'd never heard of it, but he did have it in stock tho'..
So much for their knowledge..!!
Cheers
Nish