Hi Dave
1, The size of a deflated tube depends on the make and model. If we talk about the tubes available in the UK just now, the best models are the shakespeare Expedition availablefor about £100.00 possibly £120.00 depending where you buy from.
Some tubes come with a foam padded seat that appears to be made from close cell camping type foam about 10mm thick, this is fitted between two layers of Cordura type material for the seat of the tube, this can be a little bulky to pack in a bag but it is usually not too much problem, A regular tubing mate manages to pack this make of tube into a large rucksack for any long walk into the hill locks together with neoprene waders, life jacket, fins etc. Steve Parton also makes a great tube. The Shakespeare Expedition tube was designed by Steve Parton and is manufactured abroad to keep the cost down, still a great tube though. One point to take on board with either of these tubes is that the main V hull has three seperate bladders for safety, again a Steve Parton design. The Sparton Tube also has a back rest bladder while the Shakespeare tube has two back rest bladders although I do not think that the top bladder is required as this takes up space you can use for additional gear (food, jacket, extra fleece in a small dry bag, small fish smoker etc). You can post to the USA for a huge range of tubes although with the current exchange rate, the tubes available in the UK are a good buy. I understand that Snowbee are about to release a new float tube, I have no info on this, it may be worthwhile waiting for a few weeks until more info is available on this tube before you buy a tube.
The best thing to do is to book a day at Haddo to try out a tube, Mike will sort you out and proivide any help you require. Mike may be able to source a tube for you, ring the fishery to check if he has any tubes available for sale.
2, I tube mainly with a group of friends, almost all of us have bought Vision stocking foot neoprene waders, I have had mine for five years and have walked many dozens of miles in them (not out of choice, only when walking a short distance, at most up to a mile from the car to the loch), still no leaks. One of our group uses breathable waders without any problems, I just prefer neoprene waders. I use Hi-Tec V-Lite leather walking boots three sizes larger than my normal shoe size for tubing, very poor grip on wet rocks but great for walking the hills with a tube on your back when you jump for loch to loch as we always do in the Assynt area. The leather boots provide support. If you already have wading boots they will do for a start but felt soled boots provide no grip on wet grass.
3, ALWAYS WEAR A LIFEJACKET when tubing, a bouyancy aid will not do. The collar style lifejackets are available for about £40.00. Steve Parton always advocates a jacket with manual inflation to prevent accidental inflation.
4, If you can afford them, Force Fins seem to have a good reputation, the standard Caddis style fins with the plastic strap around the heel of yor boot would be fine for a start, one member of our group has modified standard diving fins and they also work very well and did not cost the earth.
5, I would never go on holiday with a tube without a tube of Aquasure, great for mending any pin holes if you drop your tube on thorns or a barbed wire fence, it has been known to happen. You will need releasable cable ties or proper fin retainers to prevent you fins from sinking if one comes loose when you are out on a loch.
6, Most important, a friend to tube with, you should never really tube on you own, especially on the larger remote lochs.
If you have never tubed before, track down a fishery or friend who has a tube and get out on the water to see if you like it before spending a lot of money.
I am sure some of the other tubers on the forum will add their comments and experience.
You could do a lot worse than travel through to Haddo and try tubing there.
I hope you enjoy it when you get out on a tube.
Kev.