Still gathering requirements...
In terms of personal contributions v company contributions.
If you contribute £8,000 personally the pension provider will gross this up so you get £10,000 added to your pension pot.
If this is to be funded by way of you taking additional dividends then it may push you into higher rate tax. However, you basic rate threshold will be extended by the gross amount of contribution meaning that you would pay tax at 7.5% on this additional income. The resulting increase to your tax would be £600.
If the company makes a contribution of £10,000, it saves £2,000 in corporation tax so the actual cost to the company is the same as the cost to you and your pension pot will be increased by the same margin.
The difference between these two methods then is the lack of impact on your personal tax when the company makes a contribution.
Based on the above illustration it would make sense to have the company contribute on your behalf.