There's one good thing about Maurice taking umbrage at Alec sending him a telegram: at least he once and for all abandoned the harebrained idea of writing Alec a cheque! (Or giving him a bike or whatever.) That would be dangerously close to treating him like a whore, paying him for services rendered, and would probably be the end of it for Alec, who after all wouldn't take even the five shillings tip.
Maurice can be so clueless sometimes that I just want to shake him, and to so entirely misinterpret that beautiful first letter Alec wrote him as well...

I actually love the letters, they give a rare insight into Alec's emotions and the way his mind works.
The second one especially seems to me like a stream of consciousness, just laying down on a piece of paper all the thoughts tumbling ceaselessly through his head. He's desperately trying to run through all the reasons he might have "offended" Maurice, the reasons why the man who called him a "dear fellow" is now spurning him. Poor love.
Of course the half-hearted references to blackmail aren't quite so endearing but I don't blame him for being angry.

I agree with Into the Greenwood that Maurice's main emotion is panic. Never the brightest bulb in the chandelier anyway, this panic is so strong that it's short-circuited the thinking part of his brain pretty much altogether, I reckon.