Welcome, Joe. It's a matter of choice, really. And a great deal depends on how you're placed workwise. But you are perfectly correct in your assumption that, should your girlfriend be granted a Fiancee Visa, then this would entitle her to come to the UK for up to six months ... within which period, the wedding would require to take place. However, it's worth bearing in mind that, BEFORE you can even apply, you would be expected to prove to the British Embassy that the two of you have set at least a provisional date for the ceremony, and provide evidence of a reception being booked &c. In other words, proof of your serious intent to marry.
On the other hand, you might consider marrying in the Phils.This is what I did last year and, although there is divided opinion here, and consequently, some who would disagree with me, I generally recommend THIS approach ... IF, as I mentioned in my previous paragraph, you can afford sufficient time off work. Being retired, this issue was irrelevant in MY case. It is, by far, the least expensive option because, not only are most Filipino wedding receptions a helluva lot cheaper, but once married, you would only need to incur the cost of applying for a spousal visa ... thus bypassing the additional [more or less, equivalent] fees
needed for what's called 'Further Leave To Remain' if your fiancee were to come HERE [UK] to get married. Plus, a Settlement [spousal] visa would allow her to take a job in Britain straightaway, if she so-wished.
Of course, as I implied at the beginning of this post, the final decision rests with you and your girlfriend ... no-one else!![]()