In Lochmaddy, the slipway is at the "Wee Pier" or on the charts as Charles Harbour.
Is it useable in all but very low tides.
In Berneray, ferry slipways at both ends of the causeway on the east side, on the west side the is good, but no good at low water...
If you do use the west slipway, watch out for the sand bar on the south side of Berneray...the slip is good for launching for the islands on the west including Taransay and Scarp.
There is another slip at Griminish (on the North Coast), its at bit tricky to manoeuvre down as it has a dog leg...but it is useable in all states of the tide as it runs on to sand at the bottom.
The only place i've launched in South Uist is Loch Skipport...again a tidal slip...
Accommodation wise...North Uist, Langass Lodge www.langasslodge.co.uk
and Tigh Dearg www.tighdearghotel.co.uk
South Uist - Look at the Isles hotel group website...they have two hotels on Benbecula and one is South Uist.http: www.isleshotelgroup.co.uk
There is also the lochboisdale Hotel www.lochboisdale.com
& The Polochar Inn...www.polocharinn.com
Hope this helps...