My psoriasis problem?

Hey, im 19, male and from Ireland, so basically if you read my recent questions they are abut my psoriasis too, i had a problem with my scalp psoriasis, long story short i used to have to wash my hair every morning and night as it would be very tight and just scaly, i then got a job on march which meant i was always busy then with college and work (Call center) and about april and on i noticed when i woke up there was never any dandruff or anything link that, also Ireland had good weather this summer which helped it alot i didnt feel uncomfortable to walk about anymore and i never even touched my hair i always used to have to rub it as it would be itchy and sore especially in the heat but no it was perfectly fine it had all pretty much gone still have at the moment

Come September (Now) with cold weather i am now feeling my scalp get dry again not a lot but still starting to come back as psoriasis

what is the reason for this is it the sun that's good for it? and should i use the sun beds for this to see if it helps or what other reason could this be that it went away and now it is showing signs of coming back?

I would really appreciate any help or advice given!

Thanks!!