What choices you have really depends on the rules of the scheme so you should contact the trustees to be sure.
Generally, though, on leaving service before 50 you can
a. Leave paid up in existing scheme
b. Transfer to a new employers pension or Prsa (some restrictions on the prsa)
c. Transfer to a buy out bond. This is similar to leaving it but the trustee is removed. Can be claimed at 50 but some companies will have a minimum amount they will accept.
d. From age 50 to 65. you can claim the plan.
You should contact the company for your leaving service options and retirement options now.