Hi Graeme,
Sorry I missed this post and realise this is too late for your trip but if you go back (or anyone else goes) this might help.
I eat out in Ullapool about once a month and my 'go to' place has not been mentioned yet. It is the Morefield Motel which is just off the main road on the way up north. I know it is getting a little tired as a motel but the food in the restaurant has never disappointed and the staff are very friendly (and Runrig fans!). My favourite meal is the Ragout of seafood in a prawn bisque. I don't have to order it, Bev just asks 'is it the usual?' when I walk in. Well worth the 90 mile round trip for the evening.
The Ceilidh Place is also good, with a nice atmosphere, as is The Arch, which I have been to a couple of times and found to be well above average. The Ferry Bridge Inn is very good pub food, but often quite loud and busy (which isn't always a bad thing).
I too was a little disappointed with the Seaforth, OK but a little overrated. The Argyll was very ordinary pub food and I won't bother going back. I haven't tried the Indian, but have heard quite good reports.
I hope you and Mrs D enjoyed wherever you ended up.
If anyone wants any recommendations for the Gairloch and surrounding areas there aren't many places I haven't tried
Keith