A till slip shows the following information: Meter: 07032985769. Total amount paid: R1 300,00. Electricity cost (excluding VAT): R1 130,43. VAT: B. Units purchased: M. Tariff: Block 1 (0-350 kWh) at R

The meter number is explicitly stated on the till slip under "Meter:".

The meter number is $\boxed{\text{07032985769}}$.

The total amount paid is the sum of the electricity cost and the VAT.

$$\text{Total} = \text{Electricity} + \text{VAT}$$ $$\text{R1 300,00} = \text{R1 130,43} + \text{B}$$

To find B, subtract the electricity cost from the total.

$$\text{B} = \text{R1 300,00} - \text{R1 130,43}$$ $$\text{B} = \text{R169,57}$$

The missing value B is $\boxed{\text{R169,57}}$.

The cost of electricity excluding VAT is R1 130,43. We use the tariff table to find the units.

First, calculate the cost for Block 1 (0-350 kWh) at R2,19/kWh:

$$\text{Cost for Block 1} = 350 \text{ kWh} \times \text{R2,19/kWh}$$ $$\text{Cost for Block 1} = \text{R766,50}$$

Since the total electricity cost (R1 130,43) is greater than the cost for Block 1 (R766,50), Mieecke purchased units in Block 2 as well.

Next, calculate the remaining cost for electricity that falls into Block 2:

$$\text{Remaining cost} = \text{Total electricity cost} - \text{Cost for Block 1}$$ $$\text{Remaining cost} = \text{R1 130,43} - \text{R766,50}$$ $$\text{Remaining cost} = \text{R363,93}$$

Now, calculate the number of units purchased in Block 2 using the tariff of R2,91/kWh:

$$\text{Units in Block 2} = \frac{\text{Remaining cost}}{\text{Tariff for Block 2}}$$ $$\text{Units in Block 2} = \frac{\text{R363,93}}{\text{R2,91/kWh}}$$ $$\text{Units in Block 2} = 125 \text{ kWh}$$

Finally, calculate the total number of kWh units purchased:

$$\text{Total kWh units} = \text{Units in Block 1} + \text{Units in Block 2}$$ $$\text{Total kWh units} = 350 \text{ kWh} + 125 \text{ kWh}$$ $$\text{Total kWh units} = 475 \text{ kWh}$$

The number of kWh units Mieecke purchased is $\boxed{\text{475 kWh}}$.