If you join GreySpark at the management level with something to offer (new direction), then from what I could see you would enjoy working for the company. GreySpark needs this as it is small and quite new to the industry (expect to explain what GreySpark is at each meeting). It needs people who have the experience of working in the upper ranks of an established consultancy to tell them what it takes to become a true consultancy. Investment in this area is needed.
I would not recommend this company to people with less that 6 years experience if what you are looking for is a consultancy. There is no training - Management haven't got time to spend on this area. Although there are opportunities to get external training (don't expect this until after probation at the earliest). You will not know what it means to be a GreySpark consultant, because this has not been defined and they do not have their own methodology to deliver end to end projects.
If you are on the bench expect to have strange tasks to complete for management. Tasks interns shouldn't even be exposed to. This would be the perfect time to develop and learn the core skills of a consultant. Expect to learn the most from your own reading with little to no guidance.