I have a Centon K100 body and a set of lenses, along with a Lowe Alpine bag and 2 rolls of film which have been lying around in my drawer for 10 years unused.
The lenses are:
1. Pentax-M 1:2 50mm w/UV filter
2. Sigma Mini Wide 1:2.8 w/Skylight 1B filter
3. Pentax-M 1:3.5 w/1A filter
There's also a Bell & Howell MC4 2X Tele Converter
The camera and lenses were all bought 2nd hand but have had virtually no use and AFAIK are all in full working order and certainly in good condition
You'll find all of those things on eBay. Check sold listings for market prices. Might be £100 or so in total.
Not a lot, sadly. The market for manual film kit is very limited.
Centon was a Jessop's own brand camera and I don't think you will find many people looking for one. Most people will be looking for Pentax K1000, MX, ME Supers in that market.
The lens might sell well on their own on eBay but don't expect a massive return
All in my guess if it's all working and no sign of fungus in the lenses, £20-40
Try selling the filters and case separately too, package the Centon with the standard lens and split with everything else.
Optics wise Pentax lens are good. Have you thought about keeping it and taking a few photos with it?
I bought an M 50mm for £20, which seems about right.
I might be interested in the wide lens and tele converter - matt_outandabout AT hotmail.com
Just last night I sold an almost brand new Canon 300d with two zooms and battery grip for £110 so I'd imagine your 35mm kit might reach £10-£15 if it sells at all to be honest.
Have a look at http://www.ffordes.com/Commission_Sales
Email them the list and if they are willing to take it then you will get a fair price for it.