Calculate the taxable income and monthly tax based on the given salary, rent, and reliefs.

Taxable income = Basic salary + Nominal rent
$$
\text{Monthly Taxable Income} = 15,000 \, \text{Ksh} + 1,250 \, \text{Ksh} = 16,250 \, \text{Ksh}
$$

$$
\text{Annual Taxable Income (Ksh)} = 16,250 \, \text{Ksh/month} \times 12 \, \text{months/year} = 195,000 \, \text{Ksh}
$$

$$
\text{Annual Taxable Income (K£)} = \frac{195,000 \, \text{Ksh}}{20 \, \text{Ksh/K£}} = 9,750 \, \text{K£}
$$
His taxable income in K£p.a. is $\boxed{\text{9,750 K£}}$.

*   First bracket (1-2300 K£):
    $$
    \text{Tax}_1 = (2300 - 1 + 1) \, \text{K£} \times 2 \, \text{Ksh/K£} = 2300 \, \text{K£} \times 2 \, \text{Ksh/K£} = 4600 \, \text{Ksh}
    $$
*   Second bracket (2301-4600 K£):
    $$
    \text{Tax}_2 = (4600 - 2301 + 1) \, \text{K£} \times 3 \, \text{Ksh/K£} = 2300 \, \text{K£} \times 3 \, \text{Ksh/K£} = 6900 \, \text{Ksh}
    $$
*   Third bracket (4601-6900 K£):
    $$
    \text{Tax}_3 = (6900 - 4601 + 1) \, \text{K£} \times 5 \, \text{Ksh/K£} = 2300 \, \text{K£} \times 5 \, \text{Ksh/K£} = 11500 \, \text{Ksh}
    $$
*   Fourth bracket (6901-9200 K£):
    $$
    \text{Tax}_4 = (9200 - 6901 + 1) \, \text{K£} \times 7 \, \text{Ksh/K£} = 2300 \, \text{K£} \times 7 \, \text{Ksh/K£} = 16100 \, \text{Ksh}
    $$
*   Fifth bracket (9201-11500 K£):
    Mr. Ochieng's annual taxable income is 9,750 K£. This falls into the fifth bracket.
    The amount in this bracket to be taxed is $9750 - 9200 = 550 \, \text{K£}$.
    $$
    \text{Tax}_5 = 550 \, \text{K£} \times 9 \, \text{Ksh/K£} = 4950 \, \text{Ksh}
    $$

$$
\text{Gross Annual Tax} = \text{Tax}_1 + \text{Tax}_2 + \text{Tax}_3 + \text{Tax}_4 + \text{Tax}_5
$$
$$
\text{Gross Annual Tax} = 4600 + 6900 + 11500 + 16100 + 4950 = 44050 \, \text{Ksh}
$$

$$
\text{Total Annual Relief} = (\text{Personal Relief} + \text{Insurance Relief}) \times 12
$$
$$
\text{Total Annual Relief} = (1056 \, \text{Ksh/month} + 270 \, \text{Ksh/month}) \times 12 \, \text{months/year}
$$
$$
\text{Total Annual Relief} = 1326 \, \text{Ksh/month} \times 12 \, \text{months/year} = 15912 \, \text{Ksh}
$$

$$
\text{Net Annual Tax} = \text{Gross Annual Tax} - \text{Total Annual Relief}
$$
$$
\text{Net Annual Tax} = 44050 \, \text{Ksh} - 15912 \, \text{Ksh} = 28138 \, \text{Ksh}
$$

$$
\text{Net Monthly Tax} = \frac{\text{Net Annual Tax}}{12}
$$
$$
\text{Net Monthly Tax} = \frac{28138 \, \text{Ksh}}{12} \approx 2344.83 \, \text{Ksh}
$$
The amount of tax he pays per month is $\boxed{\text{2344.83 Ksh}}$.

$$
\text{Gross Monthly Income} = \text{Basic Salary} + \text{Nominal Rent}
$$
$$
\text{Gross Monthly Income} = 15,000 \, \text{Ksh} + 1,250 \, \text{Ksh} = 16,250 \, \text{Ksh}
$$

$$
\text{Net Monthly Salary} = \text{Gross Monthly Income} - \text{Net Monthly Tax}
$$
$$
\text{Net Monthly Salary} = 16,250 \, \text{Ksh} - 2344.83 \, \text{Ksh} = 13905.17 \, \text{Ksh}
$$
His net monthly salary is $\boxed{\text{13905.17 Ksh}}$.