In case you have not seen the new addition to appointment search page on UKBA website, you can now only search for 5 appointments in 15 minutes.
.You will only be able to search for a maximum of 5 appointments in 15 minutes. If you can not find the appointment you want, try again later
My interpretation of this is that the days of refreshing appointment page every few seconds are over.
However, website seems to be a bit more responsive this morning. I guess this might be a good trade off if it stays like that in the night. I will see what the response is like in the midnight.