Finally got things working pretty well.

Plot 16 was a nice result, generated by 
>> Master(10,9,-5,1,20,1,200); 
Between iterations 130-180 it shows a halo of the excess particles around a BCS condensate. For the other iterations, n_up==n_down is stuck. 
The getting stuck thing seems to happen a lot with strong interactions (large U). Unsticking them requires mu_down to get very small, near 1, which is strange considering that it should be up around 8 or 9 in the non-interacting case.

As we increase the temperature we find that the condensate starts to dissolve. The critical temperature Tc is about the same as U for small polarizations.

For polarizations like (10,9), U=-5, kT=3 condenses, kT=4 barely condenses (Delta increasing at iteration 200), and kT=5 does not condense (Delta -> 0).
For polarizations like (10,7), U=-5, kT=3 condenses, while kT=4 barely does not condense (Delta decreasing at iteration 200).  
For polarizations like (10,2), U=-5, kT=3 does not condense at all.

Higher polarisations thus make it harder for _any_ condensation to occur.  

Condensation either happens or doesn't happen - you can't get stable Delta=0.2.


Final runs:
01	Master(10,9,-1,1,25,1,2000);	Converged (25 iterations)	mu_up = 9.089844, mu_down = 8.145312, N_up = 10.008227, N_down = 9.017796
02	10	9			-3	1	1	
3	10	9			-3	3	1	
4	10	9			-5	1	1	Condensed very easily.
5	10	9			-5	3	1	Still condensing.
6	10	9			-5	4	1	Just barely condensed. (Just below T_{C})
7	10	9			-5	5	1	Did not condense -- too hot.
8	10	7			-5	4	1	Just barely did not condense. (Just above T_{C})
9	10	2			-5	3	1	Did not condense at all (highly polarised).
10	10	2			-5	1	1	Still no condensation.