请教大家，律师来信说对卖家Lease中的ground rent有疑问，要求卖方提供这个Deed of Variation：
“We note that the ground rent provisions are no longer acceptable and need to be brought in line with the current guidelines. The ground rent in the Lease is currently increased every 5 years . Please contact the freeholder and obtain a Deed of Variation”
卖家的Lease中 (2010年出的) 写着这个flat的ground rent每5年增加10%，请问这个current guidelines是指什么？现在现在每年是132磅。
If the sellers do not provide a Deed of Variation rectifying the Lease, we may be able to proceed with an indemnity policy but again, I will need to inform the mortgage company of this to see if they would be prepared to lend on these circumstances.
请问这个Deed of Variation为什么有可能不会被提供？这里需要考虑到那些要点？ 
谢谢！！