I went for the option of the Garmin 182 mono with external antenna, as well as a garmin 160 blue fishfinder.
Once rigged up, the fishfinder outputs to the gps, and the gps outputs to the dsc unit on the vhf. I am very impressed with the way all this works, and particularly the blue chart item.
Whilst going up river to Haverfordwest, I have found the chart plotter to be more accurate than following the other boats - my stainless prop only got one scratch on it from the last trip, and that was when I was turning around so well happy.
At the time, I was pondering on the 188 unit, but the cost was high, plus having 2 I thought was better than 1, so if one broke, the other unit would still work. Saying that, the fishfinder isn't much use when the gps breaks down in thick fog.... at least if there was a rod on board, it may help me find some grub (not that I eat fish).
The only gripe I have about the transducer of the fishfinder (which I assume is the same for the 188) is the size of the damn thing. When going along at 40knots, I find that it pops up every so often, and I have to pop it back down again. If the unit is raised any more, I loose all signal when going over 5knots, and if it's dropped any more it doesn't work above 10knots.
One question for Stuart though, assuming the 188 is similar to the 182, how did you get the tide tables on it? - I thought the garmin stuff only did US tide tables?