Sir Lancelot

[Khal6]

18) Strong, cool wind in Southern France (7)
20) Places where shellfish breed (6-4)
23) Given a positive emphasis (4)
26) Movement of sea which is not choppy (3,4)
27) Moderation in consumption of drink (14)
8) Period before Christmas (6)
16) Rushing suddenly in (9)
17) Become more relaxed (informal) (4,2)
21) Small banger (5)

Thanks :D:D

[baitress]

18 - mistral.
20 - oyster beds.
26 - lee tide.
27 abstemiousness.
8 advent.
16 - irruptive.
23 - spun.
17 - cool it.
21 - squib.

[Lie-in King]

Hmmm...

18a Mistral
20a Oyster beds
23a Spun
26a Lee tide
27a Abstemiousness

8d Advent
16d Irruptive
17d Cool it
21d Squib

It's nice if you can post any letters you've placed, so that people without the puzzle can more readily assist - thanks! :-)

[farmerswife]

20 mussel beds?
8 advent