HMO Change of Use. Section 106 Agreement

HMO Licensing

I think that I know deep down that I will have no option but to sign this agreement and pay the council but I just wanted to check in with you in case other landlords have had a similar issue and / or if you are aware of any legitimate legal challenge I can make ... even to get the amount reduced a bit.

I have 5 large HMO's in Guildford. To comply with my licence requirements I recently put in 5 full planning applications for change of use from C4 to Sui Generis (an expensive exercise anyway). I have now been contacted by the council to say that "Section 106 contributions will be required for the applications".

These charges relate to SANG and SAMM and come to a total- for each property- of £7,544.18. So, basically, for my 5 HMO's to be legally allowed to continue operating with their 7 or 8 tenants, I will have to pay a total of just short of £38,000 to the council.
I am now having to weigh up whether to just pay it and carry on (they are my only source of income, I am a full time landlord) or whether I am going to withdraw the applications and start issuing Section 21's to a few unfortunate tenants in order to (eventually) bring my occupancy down to 6 in each property.

Has anyone got any experience of this or any advice or suggestions other than my two perceived options?

Thank you.