Yes - if he is a CO for the purposes of the Act (The 'Armed Forces (Meaning of Commanding Officer) Regulations 2009') or has delegated authority from the CO, though his powers of punishment are severely limited. The limitation on summary dealing is that you must be 2 ranks higher. The regs state "the officer in command of a unit of which he is a member" - this would seem to cover independent squadrons but Regt company / squadron commanders would need delegated powers, I think.
also can summary dealing be used or failure to attend a doctors appointment?
As Idrach said, this would normally be dealt with on minor AGAI. However in theory it could be deemed an offence under Sect 12 "disobedience to a lawful command". Your unit should take advice from legal branch anyway.
If you are in a "normal" regt or Bn, Sub unit OC's (where of Maj rank) will have delegated powers and can deal with SSgt and Below, again as Idrach state their powers are limited, MSL (JSP830)Vol 1 Ch 13 Annex A will give you the table of available punishments for CO/OC