Wiring Baystat240a to Honeywell RTH2510 w/ picture
I'm going to base this on this manual, page 8, even though the diagram doesn't exactly match up in terms of order or number (terminal names and advice are the same). I suspect that this should work but proceed with caution. I would try calling Honeywell to verify this first

Based on the manual


Blue - Wrap in electrical tape, do not use
Brown - Wrap in electrical tape, do not use (T was not listed anywhere)
Black - Put in the W/Aux terminal with the white wire that's already there


If I were you, I'd clip some of the bare wires back to minimize the chance that they short against each other. Also, be sure to set the jumper as outlined on Page 9