This is not Tom Dunlap, but a friend Tom Murley, living in London for a few years. Fished the Spey last August, as well as other rivers. Tulchan is beautiful, but ridiculous in cost. If you really want to stay there, do so, but look to rent one of their cottages. Here is my recommendation. Stay in one of the hotels in Grantown on Spey or Nethy Bridge. You should speak to the Strathspey Estate office in Grantown on Spey for fishing. They have a few beats. I fished Castle Grant and Kinchardie (Kin Har Dee), and took one 13 pounder on the Kinchardie Beat - this was in August. These beats run about L70 ($110) per day, and there is a ghillie on the beat that helps you out. This is a much better deal than Tulchan.
You should also look at some of the smaller rivers, such as Findhorn, Conor and the Ewe. I stayed a second week in Poolewe. Beats are L80 per day on this two mile river, took 3 Salmon. Lodging in the area is much cheaper.
Don't get me wrong, the Spey is great, but production has been dropping due to gill netting and poor fishery management. If you have the big bucks for Tulcan do it, but expect to wear a jacket and tie to dinner.
For the Tweed, you should look at the attached link and book with Leeming. The tweed in great in the fall. http://www.leeming.co.uk/
Another option is Ireland, where the fishing and lodging is cheaper. The place is the Delphi lodge, run by the most passionate salmon and sea trout crusader, Peter Mantle
You can reach me at firstname.lastname@example.org for more info.