@RachelIllsley 

For us the main issue is we have hundreds of Clients and jobs set up on QuickBooks desktop and every other accountancy system seems to require the jobs to be set up as services.

For QBO, you can convert Jobs data to class or project tracking in Plus or Advanced. For Xero, you can use Tracking Categories or Xero Projects as the add-on. You will have to purchase a 3rd party conversion service.