I work for a company that has been running for nearly two years and they continue to pay us by cheque is there a legal requirement of when they should pay us, we get paid monthly.
We used to pay by cheque when we started up but later changed to BACS. Pay day is, as Bob says, as per your contract which in ours is last calendar day of the month unless as determined otherwise by the company - which gives us a bit of lee way if things go amiss!
Most young companies sometimes need a bit of flexibility with the payday as cashflow is a big factor.