When do you bring your tender perennials inside?

I was wondering when others bring their tender perennials into the greenhouse?  Right now my begonias, fuscias and verbena bonariensis are still flowering outside, and my dahlias are just starting to flower(!).  But I'm worried about the weather and keep on reading how now is the time to be digging up the tubers and digging up tender perennials to bring inside.  When do you tend to bring them in (I live in London).

Dahlias will flower up to the first frosts-they do not need lifting until then

A lot of plants will be fine for you are for a few weeks yet -the first frost seems to get later ever year-what I would do if if they are in containers is to ease off the watering in preparation- they are starting to slow down now anyway.

Keep an eye on the forecast is the best option-there is still a bit of flowering to come yet

I would not bring my dahlias in until the first frost has hit them. I live a few miles north of you and my verbenas are happy outside all winter. The begonias and fuchsias are slightly more tricky, I have just started checking the weather for frosts and will be bringing them in as soon as they look like they are struggling.

Do you just put your begonias in the greenhouse with no heating?

begonias-this is what I suggested

http://www.gardenersworld.com/forum/plants/saving-begonias/5849.html

Thanks so much for your responses and also that very helpful link!  (Apologies for the misspelling of fuchsias - I thought it looked funny!)  That's great news about the verbana - I think I'll chance it and leave it outside.  What about cosmos and salvias?  This is the first year I've grown them and not sure whether to bring them into the greenhouse.  

PurplePoppy wrote (see)

Thanks so much for your responses and also that very helpful link!  (Apologies for the misspelling of fuchsias - I thought it looked funny!)  That's great news about the verbana - I think I'll chance it and leave it outside.  What about cosmos and salvias?  This is the first year I've grown them and not sure whether to bring them into the greenhouse.  

Is that the annual red salvia?-if so easily raised from seed like cosmos-not really worth the effort-let the frost have them then dispose

You may need to post a picture of the salvia, as mine survived last winter outside

The frosts will kill the cosmos and you can grow new ones next year.

They're blue salvias and I did initially think that chocolate cosmos could be treated as tender perennials?  But perhaps I'm misinformed!  I sincerely hope that the verbana will self-seed but it's in a pot (on gravel covering concrete) so not sure it'll be successful...

PurplePoppy wrote (see)

They're blue salvias and I did initially think that chocolate cosmos could be treated as tender perennials?  But perhaps I'm misinformed!  I sincerely hope that the verbana will self-seed but it's in a pot (on gravel covering concrete) so not sure it'll be successful...

Blue salvia and chocolate cosmos is a different kettle of fish from the annual varieties

Salvia survives for me outside-the cosmos doubtful.

You might be OK with the Verbena left outside. I cover them with a thick layer of newspapers and a potfull of spent compost and they have survived the winters. They tend to come up quite late in spring. This year I covered them with a clouch and it did the trick. Like Christopher2, I take cuttings as well but haven't found any seedlings so far(must be doing something wrong)

As a matter of interest, does anyone grow wild garlic?

So muh depends upon the amount of frost we get -  until 2 years ago I left alot of things outside but after that killer winter I bring into the greenhouse alot more than I used to do.  Alliums are fine out there, as are lilies, but blue salvias, chocolate cosmos (not the annuals) need bringing in, as do geraniums, not the scrambers, they stay out and are fine,  but the pelargoniums.  Fuschias, some potted pinks, agapanthus in pots, various other tender things come in when the night temeratures drop enough for a grass frost.  I keep the greenhouse around 5 degrees when it freezes, with an electric heater.  Anything that needs more than that just has to take its chances. 

Thanks for all your posts and advice!  Really appreciate your advice.  No wild garlic for me, jatnikapyar...