I have the bench chisels and the steel seems quite good. They hold an edge better than my Marples blue chips (for what that's worth). I do have a problem with the metal rings around the base falling off, but I need to get around to taking the shiney finish off the handles, soaking the end in some water and then doing a little mushrooming of the wood to hold the handles on better. I've read something about that trick somewhere or other.
These mortise chisels might work. I'd get one and see how beefy it is. For mortise chisels, you can't have too much bulk behind it. My Narex bench chisels are a little on the light side, which is ok for most operations, but for mortising I'm more of a fan of the old pigsticker type. The only new ones I know of in that style are sold by Tools for Working Wood. Theirs are significantly more expensive, but I have heard very good things about them and the chisels are beefy enough to be around for several generations.
If money is a concern, buy the Narex ones and get proficient. Once you really know you'll be chopping out mortises on a regular basis, go for the good ones.
http://www.toolsforworkingwood.com/M...gory_Code=TBMC
No relationship to TWW except great satisfaction in the quality of the service and tools from them.