Conclusion of a letter

Hi,

If we are ending a letter with a thank you, is the following format correct:

should the line in italics be placed before or after the thanking note, if yes?

–sweng

Those can be put in either order, but the punctuation does not look right to me. Traditionally, a comma would be placed after the valediction; for example:

Many thanks,

[name]

It may be that more modern styles drop the comma, but it doesn’t look right to me to have two lines in a row without any punctuation. I think I would personally write it like this:

Many thanks, and looking forward to meeting you,

[name]

but, can and be preceded by a comma and wouldn’t that be ungrammatical?

There are times when it is possible to preced ‘and’ with a comma.
This is one of them. The final phrase is an addition and the comma denotes a separation/longer pause.
It is also valid to leave it out.