Gascoigne... I have been in your shoes and I caught my hairloss early. I am also (I was) quite hairy before I got started - Finasteride helped reduced my body hair as well (but my beard hair is the same - as good as ever). For me it too was a combination of genes from both sides of family that did it. While I am not a doctor but a hairloss "survivor" who himself used (and still use) Finasteride for 13 years since I was around 22 y.o. (I am 35 now) with great results (here's my story:
http://www.hairlosstalk.com/interact/viewtopic.php?f=28&t=69762&start=0), but I will repeat for you the advice that I just gave to another fellow kin the forum:
If you want to do something about it, you have to get on Finasteride ASAP. Here's what you do: today make an appointment with a dermatologist (preferably one that says they treat hairloss on their website), ask him or her to proscribe for you a generic Proscar (5mg Finasteride). You may want to call ahead to confirm they will do this for you so that you don't waste your time. If not, find another one that will. If you have no health insurance, derm visit may cost you (usually under $200 - or may be they'll give you a break if you tell them you are a poor student). Ask the derm to give you as many refills as possible from get go (so that you don't have to hassle with them).
Then, take your prescription to nearest pharmacist. It will cost you around $10 for 30 pills (4 months of treatment) of generic Proscar - $30 or $40 for the whole year of hair treatment (affordable enough?), depending where you live. Get a pill splitter as well. You will be splitting each pill into 4 parts (easy, with practice) and take one piece every single day (I take one every morning before breakfast - but it doesn't really matter when as long as you do it consistently).
Or, if you can afford, I would get Proscar made by Merk - to be sure you are getting the full strength of Finasteride. It's more expensive, but for me it's peace of mind (it only costs around $135 for four months of it and may be even cheaper in your area).
Also, I have a theory - the more body hair you have, the better responder to Finasteride you will be. Just a theory...
Good luck!