Complex sentence: They also added a swimming pool, jaccusi, sauna and updated the restaurant and public rooms but shortly after they sold it around 1992 to Hayley Hotels, who use it as their headquarters for their conference centre business, which they run at several sites.
Split into simpler sentences: They also added a swimming pool, jacuzzi, sauna and updated the restaurant and public rooms. Shortly after this, they sold the house (around 1992) to Hayley Hotels, who use it as their headquarters for their conference centre business, which they run at several sites.