Toilet training problems with non-communicative ASD toddler

Little man is 3yr and 8month old and was diagnosed with autism last December. 

This last week I've done a few experimental trips to the loo with him and have had some success, though I now suspect it was a fluke. He got lots of praise and a sticker to put on his bed end which he *seemed* to really appreciate (as long as I put the sticky there and he wasn't made to touch it!!)

I made the decision to start toilet training this weekend and see how it went. He's coming up to 4 years old and I'm getting a lot of pressure from friends/family to get him out of nappies especially before he starts reception next september or they may not take him!

We made a start yesterday evening after nursery and he was dry for 4 hours with one trip to the loo (sticky was given, of course)

This morning I got him up and out of his nappy, sat him on the loo and did the usual waiting game with some encouragement but nothing happened. 10 minutes after getting off the loo he did a wee on the floor. 

I expected accidents and shrugged it off, cleaning up with as little fanfare as possible. Reminded him that it would be nice if he would try to use the loo next time. 

We're getting to the end of the day and despite the fact that i have sat him on the loo every half hour, or less when I saw him fiddling, he's not done anything at all in the loo but pee'd all over the lounge instead. He's quite happy to sit in soiled underwear, he doesn't understand when I ask him to use the loo and he hasn't got the communication skills to tell me when he needs to go.

I guess what I'm looking for is confirmation that he's not ready or if you guys think he is ready to train, please can you give me any tips or suggestions at all to help get the message across. visual cards have had no impact on him up until this point either so that's not an option.