From your north Suffolk location, Molly, the only direct flights which you could easily use would be with BA from Heathrow or with Virgin Atlantic from Gatwick. Both airline's flights for next June are currently priced at around £600 return. (The exact fare depends upon your travel dates and, of course, which airline you use).
You could easily spend over £1000 for a week's accommodation in Las Vegas but, for example, the Imperial Palace Hotel (right on the 'Strip') would only cost you around £200. (Book through Thomas Cook).
Allow another £100 to eat well. So your total price is around £900. However that's based solely upon what you asked about. (Flight, food and accommodation). It excludes travel to Heathrow or Gatwick, transfers from McCarran Airport to central Las Vegas, local travel during your stay, show tickets and admission to attractions.
Chris