Dear Sideways,
I'm horrified at the answer you had from a Padang Bai dive centre... We cater for all types of divers, not just backpackers. Many divers choose to dive from Padang Bai as you can easily walk from your hotel to the dive shops, boats are on the beach just in front of the shops and it makes for a very relaxed atmosphere.
Most dive centres don't offer accommodation directly but are happy to help you out with that if you need. There are hotels for all budgets in Padang Bai and even private villas are available. Prices range from 10$ to 140$. You can find a nice hotel literally 10m from the dive centre!
The great thing about diving here in April is that it is not too busy and you can enjoy even smaller groups than usual, sometimes even private guiding. Dive centres are usually very accommodating and you can choose where to dive one day from the next.
Please drop me an email if you're still considering Padang Bai... if not, I'd still love to know who was irresponsible enough to say what they said to you (I did have a check through all our emails just in case ;-)
Best regards