Richard -

After reading your post my thoughts are that your crank is probably most serviceable...replacing the chain ring for a new one (I really like Sugino steel rings) would be a good first step.

Ofmega parts tend to be very good although are fairly unknown to many.

Little runt that I am I have still been able to bend a few lesser chain rings on climbs and you have 40 kilos on me and can probably generate some serious watts / torque.

The bottom bracket spacing probably requires a 113 - 115 mm spindle and / or a move of your chain ring to the inside of the spider... any good mechanic should understand this.

In the rear it appears that you are running a single whereas a flip flop hub would offer you that other gear you need for those longer climbs...something in the 65 gear inch range might be all you need but that all depends on your own levels of ability.

I routinely climb our city's steepest hill which maxes out at a 22% grade with my fixed mtb that runs 65 gear inches... it's tough as hell but quite doable.

That 65 gear inches is my usual working gear (especially in winter) and I have a smaller cog on the flip side that gives me 70 gear inches.

A new rear wheel should run you a few hundred dollars and some of the off the shelf units are quite good as long as you can get them checked over by a competent wheel builder.

The new SA SX3 is on my shopping list too as I want to use one of these on my fixed touring bike but a flip flop hub can be a wonderful thing.. you should be able to run a 3 tooth difference with no issues and the DA cogs are a very good choice.