HD, Frame Rates and standards

Hi All,

I am sure I am trying to oversimplify a more complicated problem but i am hoping the answer is simple..

We are working on a project that will be delivered in HD And SD Formats and used in the UK (PAL).

Some of the assets we have received to use are in 29.97 frame rates and anything we create will be 25fps frame rates.

The question is what do we build a project in - ideally we would build all in 25fps rate as the end result will be this and won't cause any problems when producing final formats. However the existing assets that are 29.97fps are rostrum rotations so any drop frames or rate changes become obviously jerky straight away.

We could build all at 29.97fps but when we come to create SD formats we are going to end up using NTSC DVD settings which is a lesser resolution and may not play on certain DVD Players.. And if we transfer at the end to 25fps we are still going to see jerkiness?

Hope this makes sense and anyones help would be most appreciated? Am i missing something fundamental..

thanks in advance to all.. we have so much work to do and need to start it but if we start down the wrong route i fear we would have to start again!..

Any help please, please