Engine temperature.

[happypug]

Hi all. Have posted a few words in the past. Can anyone advise re hdi running temperature. I have had a new radiator fitted( old one fecked) and now temp is running at 89 degrees constantly even with heater running. Previously ran at a constant 78degrees, could it be the thermostat that is not opening and closing properly anymore. Will this highish temp cause problems re head warping.
Your suggestions/cure would be appreciated.
Cheers.....not so happypug.