Best way to book 3 nights
 

I need three nights in London.
I was thinking it would better to use the B1G1 and then 1 night with points and cash, that way I save my points for a future redemption with the BOGO promotion.

Does it sounds like a good approach? and is it even possible on three consecutive nights?

I can't try yet as the points from my card haven't post on my Carlson acct yet.

I recently did a weekend in Stockholm using a similar setup.

Friday night in the Radisson Blu Stockholm Arlanda Airport, booked on points for 60k.
Saturday and Sunday night in Radisson Royal Viking on 241 weekend rate, total of £117GBP for two nights.
Definitely doable, though I did different hotels for the two different rates.

I'd say go for it.

I think it depends on the pricing. If you post that we could probably tell you what the best value would be. I wouldn't blindly use a promotion where you have to pay just to save points.