Lpc2000

I just have a small question on IRQ Interrupts...can an IRQ channel 
interrupt another IRQ routine (lower IRQ priority) that's currently 
executing?

To make this question more practical, let's say I assign TIMER0 & 
UART0 as IRQs where:
TIMER0 --> VIC Vector Control 0
UART0 --> VIC Vector Control 1

Can TIMER0 interrupt UART0 even if UART0's being serviced? If yes, 
what would be the best way to avoid possible data-share problems?

thanks in advance,
Leighton