The reset switch acts simply as an inline breaker and usually shouldn't affect operation unless it is tripped by drawing too much power. Cycling the unit on and off with a controller should work fine, as my AC's have reset switches and I've never had a prob.
Holy shit window units certainly are expensive over on your side of the pond!! They are cheaper than comparable portable units over here! I can certainly see your wanting to use a portable. However let me warn you that the BTU ratings on the portable units are generally overly-optomistic, at least this is what I found to be the case. A window unit will outperform the same BTU size portable every time. I first tried a few portables and they break too often, and generally cant keep up with anything other than a small load. Don't say I didn't warn you. I too was dead set on portables until I spent over $1000 on shit that didn't work!!
If you are in fact dead set on a portable, than you NEED a dual hose unit. The single hose unit you have pictured will simply suck the air out of your grow room. The hoses are for air cooling, in and out, or just out in the case of a single hose unit. Simply put, the unit itself sits inside the grow environment. And 1 hose sucks outside and blows it over the AC compressor to cool it, the other hose simply exhausts the hot air outside of the grow environment. With a single hose system you will be sucking out all of your CO2.
The ducted portable units will still exchange some air with the outside, so expect some smell outside.
