You are permited to start construction of the Base after you have transfered the Three Hundred (300) million credits registration fee substracted of the Fifty (50) Million Credit deposit, as stated in 5.3 - Registration Zones for Bases, Zone 2: Dublin, Manchester, Newcastle, Poole - 300,000,000 credits.
We suggest you read the 5.4 - Base Operational Regulations and 5.5 - Base Modification Protocols