OK, well, the good news is as you're from the UK, they are very less likely to view yours as a relationship of convenience. You're from a country with similar standard of living, you're obviously employable and you already have history with your families, in spite of the distance between her and yours.
A small wedding, so long as it is in keeping with your beliefs and circumstances, will not count against you. What you want to have is a clearly documented inception and development of your relationship, and what has led you both to the decision to commit and that you have a good understanding of all that is involved in your being sponsored.
Start gathering your documents, and no matter how small the wedding, include whatever planning went into it, and definitely get letters of support from both sides of the family, showing that your commitment is known, you are presenting as a couple and they are supportive.
Ask yourself, how did we explain how we made this commitment so fast to everyone who matters to us? And then put it down on paper for the immigration officer.
