Adding to what thebeast said:
HMRC's tax calculator gives £94,000 gross as a £5100 net pcm, but in fact the average net monthly income is £500 pcm higher even after you've sacrificed £6000 a year of your gross income to match the company's contribution.
I suppose this is explained by the effect of the increased tax over £100,000 which isn't reflected in your net pay because of the different way in which tax on sector pay and your allowances is calculated.
Overall, this means the real net income is actually the equivalent of earning a salary of something in the order of £120,000.
Source: Rough figures, guesswork, etc.
PS: First three months on a permanent contract always show far lower than normal take home due to wrong tax codes. Don't ask me why, but everyone complains.