It is a sad fact that many schools of WC in the UK are mcdojos.
The chisao and sparring are poor, and the concepts are often poorly taught and understood, if taught at all.
A couple of things to look out for, reiterating what others have said. Lineage is important, particularly in the UK, I know of at least two individuals who have undergone two or three years proper tuition, then set themselves up as “Masters”. There is nothing in UK Law to stop people with no experience at all fraudulently claiming abilities and teaching skills that they dont have. Well, at any rate the police are about as likely to prosecute a fraudulent kf instructor as they are an astrologer. If there is a claimed lineage, ask about it, ask to see a certificate. Maybe post the info here, so we can see if anyone has heard of the lineage or instructor.
Many lineages emphasize different things. Some are more defensive than others, some are more aggressive. If you want to learn to fight, go for an aggressive interpretation of WC. If you want to learn to defend yourself, go for an aggressive interpretation of WC. 
The school you went too sounds slightly strange, but not uncommon. Warm ups? You don’t need to warm up to do wing chun. Same for stretching, no one is asking you to kick to the head, or do the splits, or bend your legs behind your ears. You get all the circulation and blood flow you need from the forms.
Depends by what you mean by hand and leg work. Do you mean chisao? If there is no free chisao, leading to chisao/sparring, then forget it. If the school does not train in a realistic manner, then there is no point in going. If no one ever gets a cut lip, bruise, or bloody nose, then it is not worth it. You have to learn what its like to get hit, without gloves on, in a controlled environment. Otherwise, what will happen when you get hit on the street?
A agree completely with what Sihing73 said. The level of ego of the instructor and senior students is vitally important. If there are any aggressive moves towards beginners, or attempts to dominate and impress others with strength or ability, forget it. You are not entering a cult, you don’t automatically have to respect and kowtow to seniors, respect is earned, based on decent treatment of others.
Do the senior students help the less advanced, or are they stuck in a clique by themselves? Does the instructor spend time with the beginners, or just the seniors? How many people in a class? What is the ratio of instructors to students? Obviously the higher the better.
Does the instructor chisao with the students? You will be surprised at how many don’t. Does he ever get challenged?
Is there a friendly atmosphere in the club? Could you make a joke, or would you get thrown out for it? And the acid test, could you make a joke at the instructors expense? 
Is the instructor approachable? Could you ask a question about something you didnt understand? If you did, but didn’t get an answer, forget it. You are paying good money to learn a skill, if the instructor won’t teach you, why are you there?
How much time is spent training, how much is spent doing none WC related exercises, eg. pressups, situps. There is no point paying good money to do something you can do yourself at a gym or at home. If you are paying to learn WC, you should be learning WC!
And of course, there is money. If you have to pay every time you learn a new move, form, reach a “level”, or a new grade, or require a new belt, forget it. Sounds stupid? Believe me, it goes on. Be aware that some schools ask for direct debit monthly payments, personally I prefer to pay when I have a lesson, and don’t wish to have to fork out when I can’t attend.
Does the instructor teach private lessons? Providing the cost is not too great, a mixture of privates and normal classes is the best way to improve. The one-on-one lessons can give you the detailed attention you need, and the normal classes give you the yardstick to gauge your improvement, and the range of opponents of different abilities, strengths, and, importantly, heights.
And the number 1 thing to look out for? Wing Chun is kung fu, and like all good kung fu, power comes from the ground, via the stance. If they have no emphasis on stance, forget it.
If they have stances during the forms, but lose them when fighting “for mobility”, forget it.
If they emphasize upper body strength and speed rather than structure and stance, forget it.
Think of Yip Man, could you do the moves you are being taught when you are 50, or 60, and lack the strength and speed of youth? If not, you are a looking at a short term skill.
As I’m in the London area, I can’t recommend any Midland clubs, but I wish you every success with finding a good school.
Regards
Frank