Venue hire: if your average is £1500, you aint bargaining hard enough. It's as hard for venues as it is for bands which means that you can drive the prices down by threatening to shop elsewhere.
Four sound tech: venue costs will include sound engineers- whats he bringing his own for? If you're playing to an average of 600-700 people, four people is an expense you can ill afford.
£5K on rehearsals for 12 shows. Really?
T shirts profit margin of 35%. Get a new supplier. I do two colour tees screen printed tees (that makes it three if you count the colour of the actual tee) £10 with round about a 100% mark up. £3 a head is good on the merch stall though, my average is £1.