Can't see Virgin being any different to any of the other operators to the region. They use the usual airlines (Thai?) so really its about who is doing the best deal for the property you want...don't know much about the Diamond Cliff although I did look into staying there 15 years ago. Its at the quieter end of Patong, but this is a relative term as Patong is a very lively resort.

There are actually a couple of reviews on the site for the hotel.
Reviews here

Have you checked the weather for June? I think you might find quite high rainfall. Check here

Have a look at the direct pool access villa rooms of Busakorn Wing at the Holiday Inn, Patong. They are really nice and a fabulous hotel. We got to sample one the first time we stayed there (complementary) and very special. The studio rooms are lovely (and more within our budget) but the Villa rooms are a bit bigger, with complementary beer and soft drinks and dvd players in the rooms (to check out the dodgy ones taken from the back of the cinema) Although it's in Patong it's near enough to the action and far enough away from it so it's not in 'your face'. No need for transport every time you want to go out or just change money. They have a huge repeat clientèle so they can't be bad.
Hope this helps. Cheers Geri

Holiday Inn - Patong
Baan Yin Dee - south end Patong up the hill - smaller boutique hotel
Twin Palms - Surin
Banyan Tree - Laguna - expensive
Royal Meridien Yacht Club - Nai harn

Don't know if Virgin cover some of these.

No rain last June, couple of cloudy days. Saying that it can rain in one area but not another!