I just wanted to get it running, so I could drive it up to our new house and then buy a new battery when i'm feeling a bit flush. 
Well, after 2 years of the battery being flat the battery plates will have "furred" up (sulfation - lead sulfate crystals form on the lead plates as a battery discharges) The battery is in all likelyhood totally FUBARed, but I can give you a few ideas that could give you a little extra life (a couple of moths tops, really) that should allow you to save up the cash for a replacement.
Lead sulfation actually starts as soon as you remove the charging voltage from a fully charged lead-acid battery. lead sulfate crystals are converted back to lead during the normal charging cycle. The real question is, if all of the lead sulfate crystals are not turned back into lead, how long does it take before they become so hard that they can not be converted? Answer - it varies, it could be weeks or months and depends on a number of factors such as the quality of the lead, temperature, Depth-of-Discharge (DoD), plate chemistry, porosity, electrolyte stratification / levels, etc. The longer sulfation occurs, the larger and harder the lead sulfate crystals become. The positive plates will be light brown and the negative plates will be dull, off white.
In order of ease:
1)Try adding "BAT Aid" tablets to the battery cells, these are fairly cheap and do sometimes help, charge for about 72Hrs + minium. try to let the battery get to the gassing stage (the fizzing and bubbling) and let it gas for about an hour or two and top up the electrolyte levels as needed. Cycle (charge and fully discharge) the battery a number or times and the capacity will slowly begin to rise each time.
2) Apply a constant current at 2% of the battery's Reserve Capacity or 1% of the Amp Hour capacity rating for 48 to 120 hours, depending on the electrolyte temperature and capacity of the battery, at 14.4 VDC, depending on the battery type. Cycle (discharge to 50% and recharge) the battery a couple of times and test its capacity. You might have to increase the voltage in order to break down the hard lead sulfate crystals. If the battery gets above 125° F (51.7° C) then stop charging and allow the battery to cool before continuing.
3) Replace the old electrolyte with distilled / deionized water, let stand for one hour, apply a constant current at four amps at 13.8 VDC until there is no additional rise in specific gravity (use a battery hydrometer to check), remove the electrolyte, wash the sediment out, replace with fresh electrolyte (battery acid), and recharge. The sulfate crystals are more soluble in water than in electrolyte. As these crystals are dissolved, the sulfate is converted back into sulfuric acid and the specific gravity rises. This procedure will only work with some batteries.
Only to be used as a last resort:3) If the battry is badly sulfated, then it might not even take a charge, this is the worst case, and the battery is dead. There is ONE trick that might allow you to bring the battery to life again BUT this will DAMAGE the battery and it will not last a long time, but it should work for a couple of months, maybe more / less.
What you need to do is go to the chemists and get the strongest ASPRIN tablets you can buy (
ONLY USE ASPRIN not paracetomol or other pain killers, Asprin is Acetylsalicylic Acid and this will mix with the battery electrolyte to increase the acidity), you will need to drop at least two into each cell (so 12 tabs then) let it stand for about 30Mins then connect the battery charger and charge for a few hours, then check the battery voltage. continue the charge until the battery voltage read about 13.1 - 14.4V or until the voltage will not go any higher. You will prolly have to cycle the battery to get the voltage to increase, so charge it, and drain it with a heavy load (lights on the car will do nice) and recharge until the battery voltage rises.
Asprin tablets can also be used as an emergency aid to start a car with a flat battery (but not DEAD), when no other power source is available, though it will probably damge the cell chemistry of the battery requiring a new battery soon after. Handy if you leave the lights on while in the middle of no-where though!
During the cycling of the battery more of the sulfate cystals are stripped from the plates and the battery voltage and capacity will increase, but the battery will NEVER get more than 90% capacity back (more like 70%) and the voltage will remain at about 12 - 13V, not the 14.4V of a fully charged battery. The mini will start on a voltage as low as 9V as long as there is enough amps to to turn the engine over, though you will need to crank in short bursts to do so or the coil will not be getting enough voltage to fire the plugs while cranking. Doing it this way the car will fire up as soon as you stop cranking, as the plugs will spark and ignite the fuel as the engine continues to turn over a few times after the starter has stoped using all the power.
While dead bateries are generally knackerd, I have managed to get a 7yr old battery that was flat for at least 4 years to work again in my mini, and it lasted me for another 4 years.
SS
