Hi.
From my understanding, the BTech programme more or less starts off with the second year modules of the full-time B.Eng course, since all BTech candidates automatically get "advanced placement credits of 40MCs....equivalent to one year of the full-time course".
So even if you've completed a year of the part-time BTech, converting to the full-time B.Eng would mean you'd owe the (first year's) 40MCs that you had gotten free by entering BTech. And since it doesn't make much sense to start taking basic first-year modules AFTER you've completed the intermediate 2nd year (for BEng) modules, I'm guessing such a conversion is unlikely to be possible.
Then again, this is just my opinion. Sch of Engineering would have all the answers for you.