I even check dell.com/uk for some computers for him but was wondering if there were any less expensive options where he could just turn on a box and be on the internet.

He is always going to have to plug some cables in. The combination of a PC with builting Ethernet from Dell and a pre-configured router from a DSL ISP is about the easiest you are going to get, without having someone plug it all together for him.

I my experience the combination of an inexperienced user and a "cheap" PC is a receipe for disaster...

Dell do some pretty cheap PCs now anyway. Their cheapest PC (with the memory upped to 256 and a floppy added) comes out at £568.04 and that includes 3 years next day on-site service. Might want to upgrade the monitor as well though.