Hair straightening advice needed please.

[hairdisasterhelpneeded]

I've had a hairdresser disaster this week, and it looks like the only way I can salvage it until it grows out is to straighten it.
I have GHDs that I don't use that often.
What are the best products for me to use to help me 1/ protect my hair as much as possible, and 2/ try and keep the straighter effect for as long as possible so I don't have to wash it too often.

Help me feel more optimistic please!

Ok well I would use a leave in conditioning product in it when wet eg Revlon equave/L'Oréal unique1/kerastase leave in product - let it towel dry and blast dry until mostly dry then blow dry to the best of your ability after.
That way your GHDs need to do the minimal work - you need something to protect now, I like Tigi bed head at the moment, I would also use the pink kerastase serum (tiny amount on ends and brittle bits) section off and straighten.
It works for me anyway

Tresemme do a keratin smooth 7 day heat activated treatment that I've found genuinely does keep you hair straight for days/between washes.