Simplifying those steps
1. Rinse
2. Snowfoam or TFR
3. Rinse
4. 2BM wash
5. Rinse and dry
6. Wash wheels, rinse, dry
7. Claying
8. Sealant
9. Wax
10. Wheel sealant.
TBH I've done that to my own car and it doesn't take much work. Honestly, you could probably buy all you need for £100-150 and then do the work yourself if you want. You'll take more care, learn how to detail and hence in the long term, save money.
Things I would ask about:
- polishing - not necessarily paintwork correction but even a pass with a polisher and say lime prime or menzerna final finish would bring the shine out. This is the one important step they've seemed to missed out and IMO is an important part.
- rubber/window/plastics - will they pay attention to these? Windows can be clayed and cleaned. Rubber and plastics can be cleaned and dressed. They're small points but that's the point of detailing - you pay attention to detail, rather than going over the car with a sponge and single bucket!!!
- exhaust - again, small point but as above, will they clean them too?
- door and boot shuts. Will they do this? Also needs washing, drying, dressing and sealing. Helps keep the car protected (they are vulnerable areas as you get in and out of the car!) and also helps the car look clean.
- tyre dressing - don't know if this was mentioned but no point in having shiny alloys if the wheels haven't been dressed.
Ask about the above, the prices involved. I know Greeners has used Gaz from Detail My Ride. I don't know whether he or your company have insurance - what will happen if they damage the car? Personally have used Midland Detailing in Dudley as Autoperfection were a tad too far for me but both of those should be good as well.