UK licence fees will vary from £30k - £50k a year all in. Its not that much for the few large places but I guess the £30k is a lot for the small places.
I presume they pay corporation tax on the profits at standard rate + the 10% gambling tax.

The smaller places in London - maybe 10 or 12 tables - used to have maybe 50 playing customers any evening when I was doing chip runs in the past. Now these places have maybe only 10-15 players Sunday - Thursday until 10pm. Open all day but empty during the day. And the players they do have are low limit. LCI could not even make the Playboy pay.