Hey churead u alright mate?
I wouldn't go with GHS Trainwreck. I read alot about this one (and other strains) and i read alot of bad reviews about GHS' trainwreck. I think the original version is a clone only, and the closest match to it is a seedbank in canda. (don't want to spam)
You are willing to spend 30£ for 5 fems which is quite alot. imho, I would go with reg seeds, chop them males and save the money,. but i can understand the logic behind fems as well. just my 2c
As for the difference is height - there is a big difference in the strech between Indicas & Sativas when Sativas can strech up to x3, so i will suggest to SCRoG/LST them bitches to control height. Done right the end result will be a stash full of primo weed instead of just the top cola. I recommend
For Sativa, Up-Stoney High:
Jack Herer or any combination of it - Many seedbanks/breeders has their own take on this one so don't pay up for Sensi. The only down side with the Jack is longer flowering times (11-13 weeks for pure Jacks), but it is excellent yeilder. Try to look for a strain that has more indica in it for shorter flowering times.
Satori (Mandala)- If you can get them beans go for it, heard only good things. Vigorous, Heat resistant, Excellent yielder plus decent flowering times (9-10 weeks).
For Indica, Mellow-Body Stone:
AK47, White Widow, White Rhino, White Russian, Herijuana/Anesthesia - All very squat indicas with excellent yields and short flowering times. Might knock you down if smoked too much though, with the latter(s) not a party weed at all, but more for medical uses (pain relief etc)... They will make you drool over Discovery channel at 2am no probs
Cheese - No need for introduction, on all of its varieties. BlueCheese/CheeseWreck sounds lush btw
Chronic (Serious)- The guys over the pond love this weed. Super good yeilder with fat colas but i understood it lacks taste and punch?
NYCD - Yum Yum. Indica dominant, more for the flavour rather than yield.
Oooh and i forgot KillerSkunk... Sounds awesome but too rich for my blood. Plus i don't think the beans are fem or sold in packs of 5?
If you fancy being a bit of a weed snob and little bit of an adventure i will go for the Berry/Diesel/Sour combinations, but they obviously cost more and not the best yielders
I must admit i haven't tried anything like that myself but a combination of DieselxBlueberry or Jack HererxBluberry sounds too damn tasty...
All in all everyone has their own taste and preferences, i would prefer having 2oz of A+, super sticky, full flavour weed than 3oz of decent stuff...
My best suggestions is to use search option in the forum regarding all the recommendations you get, roll a phat one and start reading some grow diaries/smoke reports...
Too many strains too little time eh?
Peace my friend and happy growing

try train wreck or blue cheese , i have both going , there great , TW are tall not many leaves so better
, you can get more in ....