Looking for an Eco Friendly Garden Designer - can anyone recommend?

Good Afternoon All, I have only just joined the RSPB community so hopefully I'm posting my question in the correct way! Any constructive criticism welcome... I hope that the community are able to help me. I have recently moved into a semi detatched property in greater London and have a mid sixed back garden and front garden. The house required complete renovation which has now been completed so the next job is the garden! We had 6 leylandi in the garden until a few months ago, they were approx. 35 ft tall and had been left to grow without any maintenance and the neighbours were insistent that they were removed. The tree surgeons advised that pruning them was not an option due to their size and now our garden is very bare! I am looking for a company to design / plan the garden in the most ecologically friendly way, advising which plants, hedges, trees etc. are best to attract wildlife such as bees and butterflies, birds, and also ones that offer shelter to small mammals such as hedgehogs (I've seen one in our garden previously so I hope to give him a nice home!). Can anyone suggest a company / consultant / expert who could assist? I'm not necessarily looking to win any design awards so someone who is passionate and knowledgeable will be perfect, I'm just trying to find someone that will help me turn my garden into a haven for wildlife. Any help is greatly appreciated, Nicola