The problem is that shrubs don't usually grow very tall in containers. There are lots of small ones that are suitable, such as Japanese maples, but they won't give you flowers or a great deal of height. There are some miniature lilacs that might do. But in general, shrubs are much better in the ground.

Hi Landgirl, maybe I just need a variety of a tall and courful non toxic plant them. I love foxgloves but I've heard they are poisonous and I have a very curious kitten right now.

Buddlejas are your answer.

Seriously, they will grow to 2 metres in a 20 litre pot if fed regularly. Non-toxic, pest free, fragrant and colourful.

Only downside is that they will need replacing about once every five years.

Curious your kitten may be but he/she is unlikely to actually eat plants

Had cats most of my life and never come across one showing the slightest interest in foxgloves. Huge numbers of garden plants are toxic but cats usually know what they can and can't eat. Foxgloves won't flower all summer though. How about roses if the containers are big enough?
Actually if there were tall shrubs with beautiful flowers all summer they would be very popular! The only shrub I can think of that truly flowers all summer is Potentilla Fruticosa
Contact Wyvale Garden Centre on line and ask what their tallest ones are - a few will get up to five feet but not in their first year.

Thanks for all the advice and I'm sorry for the delay in replying. I have been a busy bee finishing off some uni bits. I am very interested in buddljas as I've seen some pictures of them and they're very attractive. In off to my local garden centre next week so will have a browse.

My cat noodle likes to eat house plants. My poor spider plant has been subjected to some bites. he is going through a chewing stage.