Hi Foggy,
First of all ask/look at your company disciplinary and grievance procedure. it should clearly state the steps taken when a formal greivance has been raised, including timescales for the investigation into the grievance.
Common practice is, upon receipt of your written grievance, 2 people will be assigned to investigate. Normally a Senior Manager and HR. They will go through your grievance and arrange to talk to you to clarify some points. This can be done face to face or via telephone.
Depending on the nature of the grievance, they may need to talk to other individuals and take witness statements, before deciding what action if any is to be taken.
It really depends on the grievance as to whether a "2 way meeting" is suitable - I have held these and all parties are keen for an amicable outcome, they can work. However, it can lead to a "shouting" match and can be quite fruitless.
The main thing is to make sure your grievance letter is detailed and accurate, includes supportive evidence where possible and most importantly, includes what you are looking for as a fair outcome.
A collective grievances should only be used if your particular grievance is covered by others. I agree with Kazza and if you have a union / or employee rep, then they could present the case.
If you want to drop me a line via FB for more support, please do. As for all HR ussues, it is better to get the full personal background to be able to advise properly.
Antm - I sympathise with you, at this satge I would advise you talk to your boss and explain you did not find their comments helpful at all. State at this stage, you do not want to take it further, but will consider a formal grievance if it continues. HR could have a "quiet" word with the colleague that started the rumour and advise them to think before they speak.
I used to work in retail and hubby still does, so can totally understand how these rumours start and escalate. Again, let me know if you want further advice off forum.
