Hi
My daughter was bedwetting until the age of 6. I really think that they have to be ready both emotional and physically, and you can't make it happen. We kept her in the night nappies, and every now and then would try her without them. Usually she would be dry one night then wet for a few nights. She would get a rash from lying in a wet bed, so we'd put her back in the nappies again, as otherwise her skin would get sore.
She too was a heavy sleeper and would be fast asleep in a wet bed. As you say, one of the downsides of having children who are good sleepers!! We tried lifting a few times but it never worked so we gave up. It was frustrating but we tried not to make her feel bad as it can be a physical issue - the brain needs to produce a hormone which suppresses the production of urine at night-time and in some children this just doesn't seem to happen until they are older.
I spoke to the local school nurse who said that they don't consider it a problem until the age of 7, when they can refer you to the enurisis clinic, so as your son is 7 you should be able to get some support. You may need a referral from your GP, and do chase them up if you don't hear from them.
Have a look at this website - www.eric.org.uk
It is a charity which deals specifically with childhood continence issues. Lots of useful information on there.
I remember reading an article in the Guardian by the American comedian Sarah Silverman who regularly wet the bed until she was 16! I also got chatting to a mum in my daughter's school who was having the same issue with her 7 year old son. That all reassured me that my DD wasn't unusual - so I know its hard, but try not to let it get to you.