Yes an email constitutes a formal offer - always ask for an email copy of the letter and contract while waiting for the hard copy.Waiting period depends on what timescale the company in question will give you. 2 weeks is reasonable, a month is pushing everyone's patience so make sure you keep in contact with the company after they offer. It is legally difficult to withdraw an offer once formally made, but they can make a reasonable assumption you are declining if they dont hear from you. Deal with recruiters the easy way - be honest. Tell them you are close to other offers, are keen to try and get some options on the table before committing. Dont tell them where these offers may come from though, just how far into the process you are. Other advice - keep in touch with everyone - the recruiters, any companies who have made an offer etc. When you do accept an offer, make sure you graciously decline the others and tell the recruiter/s, thank them for their hard work and any help, and offer to keep in touch. Do not just vanish - this will come back to haunt you should you need to move again.Finally dont rush a decision, go with what feels like the right place/people etc, and its not all about money - feeling like you will go in to work on a monday full of energy and feeling welcome is worth far more than a few £££.And well done on the offers! :)