A bare trust is just a standard document you sign. The commission / fee is for setting up the investment policy.
I'm not sure about Standard Life, but I know New Ireland have a reduced management charge on the investment if you start with a lump sum like you're talking about. A broker would be able to take you through the options available.
I've only ever set up on a commission basis, so I'm not sure what it would cost on a fee basis. I'd imagine almost 100% of policies of this type & size are done that way. But again, a broker that does on a fee basis will tell you what it costs.