How do you punctuat such sentences or is the problem just my poor syntax?

[objectivity]

Where you have an exclamation mark mid sentence. Do you capitalise the word following or not?

Best not to have an exclamation mark mid sentence, unless someone is speaking. So split it into two, with a capital letter starting the next sentence.

Do you want to post the sentence?

Can you give an example?

Well, it is from my tidy thread this morning.

So is conversational, but not speech, per se.

Aha! tidy people. BUT! witter on about tidy stuff...

I haven't a clue how to punctuate written chatty style.

It would be

Aha! Tidy people.

I'm not quite sure about the next bit -- the BUT! doesn't seem to make much sense.

I'd go for:

Aha! Tidy people. But, witter on about tidy stuff!

with the second exclamation mark optional

I think an exclamation point is not the same as a full stop. Hard to work in mid-sentence without a capital. I would have re-written the sentence too.

Aha! Tidy people! Do come over to my place and show me how it's done.

I see the whole sentence now.

I slightly disagree with lapin and would lose that first "but" entirely (there's a "but" near the end that conveys your meaning perfectly well)

So...

Ah, tidy people, I too share the same sense of well being when my house is tidy, my sheets are clean, and my ironing pile is non existent, but it still does not drive me to reach such a state.

Although actually I'd do something about "I too share the same sense" as well. It seems like a tautology.

So
"I too have that sense"
OR
"I share the sense"
OR
"I have the same sense"

You can't have an exclamation mark midsentence. An exclamation mark ends a sentence, like a full stop.

In the passage Lapin quotes you don't need the exclamtion mark for emphasis - the capitalisation of 'but' has the same effect.

Don't use exclamation marks when writing, unless to end an exclamation. "But" is not an exclamation. There are very few circumstances in which an exclamation mark works in copy, and they are best avoided. You should not really add emphasis via italics, either - it is a lazy trick. Italics are for foreign words, titles and so on.

I agree wtih Badger.

Lengthen the sentence and put the exclamation mark at the end if you really do need it (but you probably don't).

or just say 'I like it when the house is tidy, but frankly I can't be arsed'

never use too many words