Would one be mad to choose a graduate offer from Credo over grad role with a more established strategy consultancy often discussed as a candidate for "Tier 2" with the Oliver Wymans of this world?

It depends. Although there is a definite uptick in the market we are not out of the woods - yet. If you have an offer in hand from a credible firm it's better to take this than hold out for the possibility of something else - all experience is good experience.

selecting - I would be very wary of going with a boutique at the moment. To be too specialised in the current economic climate risks the work falling off and you being back looking for a job.

selecting - do you have an offer both from Credo and from another Oliver Wyman like firm? Or do you have an offer from Credo and are considering whether to try and get an Oliver Wyman like offer instead? Not clear from your post - but massively impacts the advice I'd give!

Sadly your question is not phrased in any version of the English language I am familiar with, which is why it is difficult to provide advice. Depending on what the question is, one answer might be: “ go for the big brand name: you can always move from a large firm to a small firm later in your career but it is very difficult to move in the other direction”