Holidays.  Your annual leave should be quoted exclusive of public holidays, or else your 25-day quota might really equal 17 days. 

Notice.  Take as much notice as you can get.  If you are worried that a long notice period will harm your chances when the time comes to move on again, ask for asymmetric terms - they have to give you six months' notice but you have to give them only three months, perhaps.  Obviously, you must consider the effect a period of gardening leave could have on your client relationships.  When you resign, you must offer to work your notice period. If not, the company can refuse to pay you for this period. They can only make you work your notice as gardening leave if there is a clause in your contract allowing them to do so. If not, you can insist on going into the office.

Restrictive covenants.  These place restrictions on you for a certain period after you leave a job, this could take the form of 6 or even 12 months.

The 4 main types are:

Non-dealing.  You must refuse past clients if you are approached by them.

Non-solicitation.  You may not approach past clients for business in your own right or that of your new employer.

Non-competition. You cannot work for a competing company during the specified period.

Non-poaching. You may not offer staff from your old employer jobs with your new one.

Job title.  Make sure it is specific and make sure you are happy with it before proceeding.  Tighten up on words that could be widely interpreted, 'other duties' comes to mind or 'as required by the company' give your employer the option to change your job as they wish, no matter what you wish.

Armchair experts.  Go and see a specialist Solicitor. 

Probation periods.  Usually these specify that you need be given only one week's notice of termination during the first three to six months at a new job. They are used by employers to limit their liability on trainee hires usually.  If you're coming from a good job with a solid billings record you don't have to be tied to a probationary period and could negotiate to have this shortened or removed.