I'm currently in quite a low paid job, £34k as a senior .NET developer. I (stupidly) gave away my salary to a recruitment agency whilst applying for a new job. The salary range of this new job is £35k-55k, they are offering £40k but I have insisted on £45k-£46k (£45k is the median and is the market rate.)

I'm quite comfortable where I am and I've applied for four development jobs in my life and have never been rejected, so I'm quite confident that I can get a job at £45k elsewhere. However this company seems like a nice place to work, is close to home and has a lot of room for career development.

The recruiter is going to speak to the account manager on Monday. If they continue to low ball me then I'm thinking of just telling the recruiter that whilst a 32% increase might seem like a lot, I can always walk in to a different job on a similar salary but with a different recruiter that does not know my current salary. 

Am I being a little too forthright here or is this an acceptable tactic?