Yeah, extended and instant release. They're often prescribed together that way for chronic pain.
To be honest, it's really a matter for you and your doctor. Be warned, doctors can smell drug-seeking at a gazillion paces and - given your recent thread about wanting to try heroin - this does have a faint whiff of it even to me. That and in the OP you ask what the difference in analgesic effect is between morphine and diamorpine then go on to say you were given sub-q diamorphine for pain in the past but don't include it in your list of prescribed meds.
I'm not casting aspersions cos I have no idea what your situation is but there is definitely a drug-seeking waft around the place. I'm not suggesting that you are not in need of proper pain control meds but you need to be careful when dealing with doctors cos they will cut you off dead and prescribe fuck all forevermore if they also catch that waft whether there is legitimate need or not.