Just for my two peneth worth my first step in your shoes would be check what the exact situation is, e.g. if you start work and after three months you go on adoption leave after a further three months (six months into your contract) would you be eligible to claim any adoption leave pay going forward from that point?
Can you talk to your social worker about how likely a match would be any time soon? You do not need to say why.
We met our son almost 8 months after being approved. If you were approved in January and took the same amount of time as us to be matched you would be August and presumably would have only been in your new job a short while. But if you took a year (as I have heard is perhaps quite common now) if you started your new job by June/July and then were matched and going on adoption leave by January, then you would be OK to get the adoption pay - wouldn't you?
What kind of child are you hoping to adopt? A baby, older child, siblings? Your social worker should know how likely your desired match may be to come up in your area.
Can you afford to lose that adoption leave pay (do you know how much it is worth - just check out the amount based on your current salary - because if you stay in your current job that would be the salary it was based on).
One last question, do you envisage going back to work after adoption leave? If so, would you go back part time? Which job may accommodate this better?
I in your shoes would say if you could afford to be on unpaid adoption leave and really hate your current job and really like the look of the new job, I would go for the new job. Leave your current job as fast as you are allowed to and get started as fast as you can on your new job!
If you do not plan to go back to work after adoption leave I would stay put because it is less of an issue IMHO.
I feel the easiest thing might be to delay matching by six months but personally this is not something I would want to do. So I would either suck it up and do my horrible job now and look forward to a quick match, or I would go for it with new job if you can afford to be without the leave entitlement.
I guess the delaying by six months would be like being on a break. We took a short three month break at the start because we had a lot going on and we were told it was easier to slow the process at the start than at the end. The only danger with delaying at the end is how frustrated you get while waiting and knowing that any good matches that might come into your area you would not be able to go for because you would be on a break!
Good luck, please do tell us what you do! 