Here's the completed advertisement:

The town of Keswick, (1) **which** lies at the heart of the Lake District, is the perfect place for a holiday, and the Derwent Hotel, (2) **which** overlooks the town, is the perfect place to stay. Robin and Wendy Jackson (3) **who** bought this small hotel 3 years ago, have already won an excellent reputation. Robin, (4) **whose** cooking is one of the reasons (5) **why** the Derwent is so popular, was once Young Chef of the Year. The comfort of the guests, (6) **whom** the owners treat almost as members of the family, always comes first. Peter Ustinov, (7) **who** once stayed at the hotel, described it as "marvellous". And the Lake District, (8) **which** has so much wonderful scenery and (9) **where** the poet Wordsworth lived, will not disappoint you.