Hi, Rauf,
I've just finished a project using the LPC (767 in fact, but it doesn't matter) and I have a very good impression. As for the difference between EPROM and OTP in reality it does not exist, as EPROM means technology (Erasable Programmable Read-Only Memory) and OTP (One Time Programmable) means that there is no window to erase the memory through it. But I heard about several cases when the LPC were erased with X-rays. I do not think you could find something like this with flash - I tried but failed.
Regards,
Michael.