I'm sorry to hear you are experiencing these difficulties. I haven't personally experienced SAD, but from what you describe, it seems to me like it must be really challenging to be aware of the cyclical nature of how your mood alters with the seasons, particularly when you feel yourself being "drawn in" to a low mood or a dark place. On the up side, the way you describe your situation makes it seem to me like you have really good insight into your emotions and feelings about this, and it sounds as though you are very "in touch" with what you are experiencing, if that makes any sense.
I have to say, based purely on the detail you provided in your post, I'm not totally sure that I buy what your GP has to say about counselling not being available for free on the NHS. Counselling and other talking therapies are provided by the NHS in the UK, and recently, there's been quite a big push towards expanding this (if you are interested, Google "IAPT" (Improving Access to Psychological Therapies)). Undoubtedly, there is still much work to be done, and there is considerable regional variation as to the availability of services, but in most parts of the UK, you should at the very least be able to access things like low-intensity CBT or guided self-help resources, if you have received any diagnosis of a mental health problem. Of course, it also depends on the nature of your personal case - for fairly "basic" cases of things like mild depression and anxiety (if there is such a thing as a basic case!), there is more help available, but for more complicated problems, particularly where there are multiple difficulties in various domains of a person's life, longer term psychotherapy may be more suitable, and undoubtedly it is quite challenging to gain access to this on the NHS. Having said that, the way the new model of delivering therapy services in the NHS works is through what's known as a "stepped care" system - you tend to start off with a relatively low-intensity form of treatment, and then you get "stepped up" to progressively more intensive (and commensurately harder to access!) services, if your difficulties aren't adequately addressed by lower-intensity interventions.
If you feel like you might benefit from some form of talking therapy, it might be worth having a look around on the internet for NHS therapy services in your area and approaching your GP again with this information. I'm really happy to talk with you more about this if you would find it at all helpful. I'm not a professional therapist or anything like that, but I am studying for a PhD at the moment in clinical psychology, and I am based in a research clinic for depression and anxiety, where NHS patients are referred to for various types of talking therapy. I'm not massively comfortable talking about stuff relating to my work on a public forum, but I'd be more than happy to continue the conversation in a PM, if you are at all interested and would find it helpful. No worries if not, I don't mind at all
