A nice hotel around 70€ per night?

Retail price for Hotels in HK can be very pricey, well above 70 euros a night.  Your best bet is to use Priceline.  I once got a 5 star hotel for 120 usd.  Otherwise, your best bet is to use a site like agoda.com and book a boutique hotel, those most likely will not have breakfast, but you're in HK!! There's food everywhere!

Maybe check the Dorsett Mongkok hotel, it's a 4-star hotel and I stayed there last time for around 60 euros per night (without breakfast) by booking in advance.

IHG has a friends and family promo.  Just google "IHG friend and family" and book w/ that promo rate.  Don't have to be an employee or family member to use that rate.  Holiday Inn Golden Mile in TsT or Crowne Plaza Hong Kong Causeway Bay in CwB should be around that rate.