Shipping charges

Hi Folks,
Im wanting to create a series of shipping charges based on a shipping flag in the database for a given product..
I need to create 3 charges and they are as follows:
1 - £0
2 - £10
3 - £25

Basically it has to work like this:
If someone places an item in the basket that is shipping 1 then it has to stay £0. If they then add something that is flagged as shipping 2 then it needs to show £10, if they add another shipping 2 product this then needs to add another £10 shipping to the cart. If they then add a third shipping 2 product it needs to default to £25.
If there is any 1 item that is shipping 3 placed in the basket, then the whole basket shipping charge from there needs to be £25 regardless of how many other products from other shipping categories are added.

Our company has a shipping process of a flat £25 fee for all items apart from accessories which are £0 shipping, however we have introduced a carrier company who charge £10 per item on specific items. We as a company will absorb any shipping costs over and above £25 from a carrier on these given products.

I hope ive explained what im trying to achieve and I hope someone can help point me the right direction.

Cheers

Paul