No, you don't have to choose a tree for deep shade - just make sure you buy one that's at least 3 feet tall from top to bottom before planting, taller if possible. It'll be potgrown if you want it this time of year, so don't include the pot in the 3 foot measurement...
And don't worry about the questions - the way the weather is this year, lots of questions are good - keeps me occupied on these grey, chilly and gloomy days

Thanks Bamboo:-) I know just what you mean about the weather .I must have around thirty plants waiting to go in but if I go charging in on my sodden clay I'll just ruin all the structure of the soil I've worked so hard to improve .Its so frustrating ! :-))

I have a three year old Viburnum Plicatum Mariessi that I have no home for .I thought about trying that as its a large corner and it would have plenty of space .At the moment it does get a small amount of sun in the height of summer and when I prune my climbing rose back .Possible ?

That would take the sun/shade conditions, but it does get rather wide. Ours is a good 6 feet across at the base, obviously getting progressively narrower as it gets taller.

If I plant it in the centre of the corner Owdboggy it has a good 5 ft either way for the branches to spread out and do their thing (just measured ) and unlimited space at the front .:-)

I'd use it there if you've nowhere else for it ,but make sure you plant it with plenty of room behind it so it can spread all round.

I've added a photo of the area :-)There are two more trellis to go up behind it to screen my neighbours greenhouse but it would be planted where the washing line is positioned so quite a large area for it to spread .I do love them but they need space and this is the only area I have for now .

I'd say that's room enough - I must admit when I saw the photo, my first thought was that washing line will need to be moved, lol!

I dont think I've ever used it as a washing line as I have one in my little courtyard but its great for planning shrub positions lol