Well, don't worry too much. Once you have put in your 'Part P' building control notice for the works and paid the fee to the council, you'll get a building inspector (or appointee) come round and you can discuss with them what is acceptable. They then come back after first fix and again for commissioning.
If you are just changing the CU, there might not be significant savings DIY. Essentially, you'll be paying for an electrician either way.
If you are just changing the CU, there might not be significant savings DIY. Essentially, you'll be paying for an electrician either way.