If you want service in the army to be a part-time job, the Territorial Army (TA) is the option for you. TA soldiers keep their day job and do military training and camaraderie in their spare time. Depending on the unit and work TA soldiers do, this could be a commitment of 19 to 27 days a year. There is also a two week training camp each year. While less so than the Regular Army, there is a chance that those in the TA will have to serve for a "tour of duty" overseas at some point. By law, your day job is safe when you must be pulled away for training or a tour.
Members are paid for time spent training and bonuses are paid for reaching certain milestones on the amount of training done each year. For the first year, that bonus amount is £424 and £1674 is paid after five years of service. At this time, a new soldier recruit will get £35.04 for a full day of training and that amount will increase to £43.54 once basic training has been completed. Those that become a TA officer will receive £62.07 per day of training after basic. With each promotion in rank, the pay will increase.
Becoming a Territorial will give a person training in military skills, trade/career skills (including certifications that will help in the civilian workforce), important life skills, and experiences one can't get otherwise. Take advantage of the free training that will help your CV and job prospects. Stay physically fit with the help of your TA unit's physical training instructor. Learn to deal with others, manage time effectively, and demonstrate to potential employers that you are skilled and motivated.
TA soldiers are not committed to serving and can quit at any time - other than when mobilized with your unit on a tour. Just talk to your commanders and once they ensure you really want to leave, they'll explain the withdrawal process to you.