How to act infront of recruitment agency?

I am multi skilled, can drive lorries of any size (but no experience commercialy), got a degree in construction, and was an engineer workin on heavy tracked vehicles for 5 years. i have paperwork experience etc, and fully capabale all sorts of softwares including autocad and microsoft office. whenever i go to the agency, they always ask what i want to do, i always say anything because i am literally multi skilled, is this so hard to believe? but they always turn me away!! or when i say lorry driving, or engineering they always tell me to apply online. why? clearly they got it advertised and people apply by hand, not just online! when i was down south during my degrees getting a job through agencies was easy, up here in the north (manchester) it is much much much harder. I always wear trousers, shoes and shirt with tie. what am i doing wrong?? if they ask again what do i want to do, what should i say? is there some kind of key word, for example should i say 'industrial' so it doesnt confuse them when i talk slightly out of their language? i guess arriving on the friday afternoon isnt a good time, perhaps monday mornings at 9 then! please help me, i dont want to apply for job seekers!!! this question is UK based