SOLVED - Need help on shipping options/extensions

I want to implement a shopping cart value based shipping option. This is to complete effectively with our competitors who charge a basic sliding scale based on the cost of the cart.

However, I then need to add options to add special service costs such as next day, air, 3 day etc. Some services like next day air is charge at $$ per 20lbs weight.

In addition some BIG/Heavy items cannot go by normal shipping, and have to go road freight so if these are added to the cart, I need to add the cost of road freight.

I seem to need a combination of value based and product based shipping, plus some custom shipping options the customer can add if he wants an enhanced delivery service.

Summary:
1 - value based shipping as standard (<49.99=$5, <99.99=$10) etc on the standard cart contents
2 - add road freight option if an item is over X lbs in weight (this would be in addition to the shipping cost in point 1 unless it was the only item)
3 - Present some fixed costs for enhanced/upgraded shipping speed

This sounds very complex to achieve with the standard OC options, but I am struggling to extensions that will achieve what I need.

Suggestions please

In the end we implemented this:

Value based add on from Clear Thinking. No core mods and works without problems, and was dead cheap. This we used to give our standard shipping rates, and free shipping over 250 bucks.

UPS mod to allow us to hack a discount to make us competitive with our competition. Free from developer colosports.
We have negotiated rates with UPS so needed to add a % discount to the rates returned by the UPS server. This gave us our upgraded options for 2nd day and next day etc. Not exactly what I wanted to achieve, but with hours of simulations we hit on a formula to keep us in profit, but to stop us losing sales due to expensive shipping.

Finally we used the weight based shipping for far flung destinations such as the 49th and 50th states. This stopped us over discounting shipping to Alaska and Hawaii etc. However UPS is so so expensive for those locations, we will add USPS as an option for them.

Hope this helps someone one day, as shipping has proved to be the most complex and agonising activity we have gone through in building the new store.