They can't refuse it without having the meeting so they have broken the law (i have copied the relevant stuff below). But I do think you will have to go to work on Monday, unless you can get signed off sick...?
Your employer must arrange a meeting with you to discuss your request within 28 days of receiving your request, although this time limit can be extended either if you agree to an extension or if the person who has to make the decision is away on leave or is ill. You have the right to be accompanied to the meeting by a worker employed by the same employer (this can be a trade union representative as long as they work for your employer too).
Fourteen days after the meeting your employer must give you a decision in writing. S/he may grant your request; refuse to grant your request but permit an agreed compromise; or refuse your request altogether.
A request can only be refused on one or more of the permitted reasons. These are:
Burden of additional costs
Detrimental effect on ability to meet customer demand
Inability to reorganise work among existing staff
Inability to recruit additional staff
Detrimental impact on quality
Detrimental impact on performance
Insufficiency of work during the periods you propose to work
Planned structural changes.
As well as stating one of the permitted reasons, your employer should explain how they think the reason applies to your circumstances. So, they cannot just say ?I reject your request because of the burden of additional costs ? they must follow that up with some more detail on how it applies to your particular request. If your employer does not give you reasons in writing or does not explain them, you should ask him/her to. Knowing the reasons you have been turned down for will help you to appeal, if you want to.
You have 14 days from being given the written reasons to appeal the decision. If you do appeal your employer must organise another meeting 14 days after you have made your appeal in writing. You can appeal on any grounds. For example, your employer may not have taken something into account when he/she made the decision or you may want to challenge the business reason s/he has given you.
14 days after the appeal meeting your employer must tell you whether or not your appeal was upheld. Again, this must be in writing and must give reasons. If your appeal is not upheld and you want to take matters further, you should raise a grievance (see below).
from: www.workingfamilies.org.uk/asp/family_zone/fs_fw1_flexwork.asp