Lansdale officials say the borough books for the year that just ended will show a $300,000 surplus.   That's a big change from just a month ago when a break even scenario appeared likely.   Borough officials say the receipt of some last minute grants is partially responsible for the surplus.   They also say operating expenses in some borough departments came in lower than expected.   The borough started last year with a budget deficit in excess of $785,000 and tacked on more expenses by firing one borough manager and hiring another.   The borough saved about $600,000  by refinancing part of its debt.   Revenue was enhanced with increases in charges for sewer and electric service.