Hi Sue,
Yes, we are talking about the same individual. I didn't find Mathew, but it is over six years since I was researching this William Asher so maybe he's been added lately. I think it is very likely that Mathew is also a child of his, as I have a copy of William's 1826 Discharge Papers I got from the National Archives. In addition to his back-pay he received a Travel Voucher for himself, wife and four children to get from London to Glasgow where he originally signed up. I had found only three children for him born before 1826:- Alexander b. 1814, Martha b. 1823 and William b. 1824 so the fourth could well be this Mathew. He isn't with the family in the 1841 Census, though, so may not have survived until then.
I have a lot more information about this William, his parents, his siblings and all their families which I can send you. To save duplicating research you have already done can you tell me what areas you want to know about?
Regards, Alastair MacDonald