I babysit for some twins (have known them since they were very small, now they are 21 months old) in Windlesham. Will send their mum an e-mail and see if she can suggest any groups which are twin specific.
Meanwhile, Woking Twins Club holds a Parent & Toddler group in Knaphill on Monday's 9.30-11.30 St Hugh of Lincoln Church (Parish Room), Victoria Road, Knaphill GU21 2AA More details...
If you want more general toddler groups then:
Drop in group run by NCT. Every Monday 10-11.30am (closed on Bank Holidays)
Holy Trinity Church, Church Rd, Sunningdale, SL5 0NJ
St Michael's Parent and Toddler Group
Wednesday 10am- 11.30am
St. Michael's Church Hall, Church Lane, ASCOT, SL5 7DD
Sunningdale Parent and Toddler Group
Tuesday from 10 - 11.30am
Baptist Church Hall, High Street, Sunningdale, SL5 0NG
There is also a Coffee & Chat group that meets at Sunningdale Venues / CMI Rendezvous Cafe at 10.30am on Fridays.
I went to a toddler group in Bagshot on a Wednesday 9.30am-11am at St Annes Hall, Church Road, Bagshot, Surrey, GU19 5EQ for many years when I used to nanny on a Wednesday (currently I nanny Mon,Tue,Thur,Fri).
I found that I had to experiment a bit with baby/toddler groups to find ones which fitted with me and the children in my care. So once groups restart in September, visit a selection in the area and see which you and your twins like.