Hello Sunshine,
I think firstly, you have a duty and responsibility to be truthful firstly with your fiance to be, it will be worse if you don't come clean, and then your fiance, finds out, that you have indeed not been truthful.
No matter how you may feel embarassed about your past application and your relationship with another foreigner, your policy of withholding information from the man you are supposed to be in love with, is in itself highly reprehensible.
If you love this guy you will tell him the truth, and if he loves you, he may be mad at first, but only at first, and may even say, ok you told the truth, lets start afresh and move on.
My advice is to come clean and tell your British man the whole truth and nothing but the truth, or you run the risk of having a very bad foundation for your relationship.
My second point of advice to you, is under no circumstances should you seek to withhold information from our Government, nor should you seek to feel you should be untruthful when answering questions on a British Government application form, you will be asked that question, if you have ever applied for a visa for another country, you should state plainly, that you have, and you should also state that the application was denied.
With Entry Clearance Officers honesty is your best policy, at least then, you have told the whole truth, and nothing but the truth, and you never know, your previous application may be ignored, but if you fail to provide the correct information or tell lies in your application.
Any person caught doing so, will be immediately banned from applying for UK Entry Clearance in any capacity, whether it be tourist, fiancee, or spouse, for a period of 10 years.
Do you really want to run the risk of that ?
Think carefully before you act, whilst writing on this thread, I really do sometimes feel annoyed at ones like you, who seek to circumvent our Countries immigration policies, and procedures by trying to canvass for support on this web site, and hope that someone will give you a speck of hope that the action you want to take is ok, and somehow a legitimate way of conducting yourself.
When it comes to your authorities, we as foreigners cannot seek to mislead the Philippine Bureau of Immigration, and are dealt with harshly if we choose to ignore your Governments policy regarding overstaying, or other matters.
I would caution you to act wisely, the fact that you seek to defraud your fiance out of the truth, that previously, you have been the subject of a visa application to go to another country, leaves me to form the opinion, that you are most probably a serial applicant, hoping that one application or another goes through and you end up in foreigner land !
Tell the truth young lady, and you might just make it.....