Weight / Fat loss

Hadn't spotted this forum>thread before, so far been very useful just plodding through it.

Until now I've never had a problem with weight, I could do what I want, live how I want, eat what I want when I want and only excersize was purely for enjoyment (gym sessions were only to keep in touch with mates etc).
But now I'm pushing mid 20s I guess my epic metabolic rate is failing me. Though for the past 5years I have been MUCH more careful around processed foods/ salts/ sugar (Used to be a cake fiend) which has probably done me well until now.
My 'about right' weight is 70-75kg (~11st), I'm 5'9" light built up top (though used to have good shoulders and back from rugby from 12-19yrs) but heavy built legs (skinny jeans can >>>>>>>).
I've always cycled a fair amount and I do notice being a bit lighter in summer from more miles and stocking up after winter but never this much.

Figure not having a full time job/ point in life means I currently eat a GOOD deal less food (volume/calories/crap content) than I ordinarily would, but not having a structured day/ week means I am doing far less than ever before.

Last summer was nudging 80kg, then lost a bit towards this spring (april'11) then this summer wasn't too bad as was bashing out about 450-500miles a month riding on my own and in groups on road bike and lots of long distance dog walking (all day jobs getting ragged around 'fells by 2x fit & boystrous border collies).
End of summer till now (sept > today) gone from about 80kg - 88kg VERY quickly. Dunno if I'm going crazy but can almost feel the fat jumping on by the day, yet I eat next to fuck all (only crap food being a smattering of peanut butter in mornings).

Bit worried about it TBH, almost feel I am at a tipping point, i.e. if I start gaining more now, by spring I'll have too much on to be able to move it again and how bad it is for me.

Only recent change is essentially stopped riding, I'm back down to what I used to do, i.e. ride when and how I feel like it on my own, on MTB and for random distances/ exertions. Stopped riding with yet another club after being literally left for dead on a mountain pass in pretty much a rain storm (50mph+ winds gusting more, rain so bad cars were pulling over) and very nearly got into serious trouble in a remote location; and since then just CBA'd to ride road anymore, too many wankers.

Wonder if anyone has had similar issue? Basically how do I go from here, need to kerb the weight ideally without riding, I used to fellrun but thanks to a pair of good knee injuries unlikely I can take that up again.

Got even worse since that post, can't even remember last time I picked up any bike, must be at least a month, maybe more?
My work is now a cheeky 2miles from home, so you'd think I'd ride or walk it right? Wrong, been driving it, urgh.

I can actually feel the fat building by the day.
though I am decreasing food input too.
Just cannot get motivated at all, playing on ebay and thinking of just selling road bikes as they aren't getting used any more (spent more time building them than riding them lol), the 'other' roadies around here are all well up themselves, don't really want to be associated with them TBH.