Wel to my surprise, one of the companies that I asked to quote has been to look already and here is the result. Your comments are invited

The three trees, two in the back and the one next to the garage, should be removed as the two larger specimens have attained a size where sections are liable to failure in extreme weather. The tree adjacent to the garage will continue to have an impact on both the drive and the structure of the garage if left to grow. Removing the trees will have no effect on the structure or foundations.
The trees forming a hedge along the front boundary are starting to interfere with both the footway and streetlight and it will be probable that the city council will ask you to trim them accordingly in the near future. Some form of management will be required. It is your decision as to whether you would like to retain them as a hedge or remove them. I have quoted for removal.
• Very large Leylandii in rear garden at far end. To fell to ground level our charge would be £480.00+Vat. To grind main roots to 150-200mm below ground level our charge would be £95.00+Vat.
• Leylandii in rear garden at far end near the large tree. To fell to ground level our charge would be £85.00+Vat. To grind main roots to 150-200mm to below ground level our charge would be £35.00+Vat.
• Leylandii by garage. To fell to ground level our charge would be £350.00+Vat. To grind main roots to below ground level our charge would be £85.00+Vat.
• Leylandii x 5 along front wall. To fell to ground level our charge would be £175.00+Vat. To grind main roots to below ground level our charge would be £90.00+Vat.

Redg