I'm not sure what extra cost was incurred running the AC 24/7 rather than night time only as it meant that the doors and windows were closed so it only needed to maintain temperature rather than cooling the room down every day (open doors and windows during day usually to air).
However, the most important bit is that I tasted the beer last night and it is fantastic!! So it appears that fermenting for 2 weeks in a room maintained at around 73 degrees (measured near fermentor) did not make the beer undrinkable. I can't say whether it would have been any better if it had fermented cooler but the beer is really good - if I had a bottle of it in a bar, I would happily order more as its better than many I've drunk when I've been out (and certainly beats what I can get locally).
In case it helps anyone else (including chuffy2), here are the details (including mistakes I thought could cause problems):
1) DME kit of Our Special Holiday Ale (21B) from Austin Homebrew (anchor clone).
2) Didn't have a big enough pot so split between 3 for hop additions and hops divided accordingly (
https://www.homebrewtalk.com/f39/help-i-dont-have-big-enough-brew-pot-278196/#post3470005)
3) Added the "gunk" (can't remember official term) from the pots to the fermentor. Actually made an effort to include it, didn't realise it should stay in boiling pots!
4) Used Muntons premium gold ale dry yeast and BrewVint yeast fuel
5) Temperature control was putting a room thermomenter near the fermentor and maintainign room at 73 degrees based on thermometer. Also put femrnting bucket in a tub of water to minimise any temperature fluctuations and hopefully conduct any produced heat away from fermentinfg bucket.
6) Left it in primary fermentor for 2 weeks exactly (didn't have hydrometer to test it but instructions said 5-7 days in primary followed by same in secondary - and yes, I was one of those people that panicked that I needed a secondary even after what people here said -
https://www.homebrewtalk.com/f39/how-long-primary-if-no-secondary-279288/)
7) Tasted OK when bottling but a bit too hoppy and pretty cloudy
8) Bottled in combination of bottles ranging from 11.5oz red stripe stubbies to 19.2oz cider bottles and everything in between (although all but one were brown glass)
9) Bottled one in clear glass so I could see how it was progressing (ie whether it was clearing). Can't remember where I saw/heard this tip but if I find the link I'll give credit where credit is due.
10) Bottles left in a covered plastic box (to contain any potential bottle bombs) in an unconditioned room (78-80 degrees) for 3 weeks exactly. Didn't open box during the three weeks but that was because I was away, not sure I would have had willpower if I'd been at home!
11) 1 night in the fridge then tasted and it was fantastic. Now to see how it improves over time (some in fridge, some still in plastic box).
A bit of a long post but I know that all the advice I got on this forum really helped me so wanted to post some feedback as a first time brewer. As the phrase goes RDWHAHB (even if it's hard to relax becuase you think its gone wrong!).
Next stop, chest freezer, temp controller and a bigger boil pot, ingredients for batch 2 already on dining room table!!