Les Brown’s side are now guaranteed to finish in runners-up spot behind second division champions Trafalgar Reserves, in just their first season together.
“Im very pleased that we have achieved promotion at the first attempt,” boss Brown said.
“We set off like a train and I think that had it not been for bad weather and cancellations we would have pushed Traf Reserves closer. We didn’t play a single game in almost three months around Christmas and that stopped our momentum.
“The lads have done me proud, however, and I’m happy to be promoted and have reached two semi-finals and a quarter-final.
“We already have new players keen to sign next season and I’m confident we will hold our own in the top division and go from strength to strength.”
Both FILO and Alma struggled to get to grips with the windy conditions on Thursday evening and there were no goals in the first half, although the home side did have a man sent off.
FILO’s Dan Brown opened the scoring against the 10 men after the break with a back-post header, and the visitors netted two more goals in quick succession through man of match Jordan Purvis and a tidy finish from Phil Spencer.