the tower of London is two times as high as the Church tower

这种用法是对的
用英语表达“A 是 B 的 N 倍长（宽,高,大,重等）”,“A 比 B 长（宽,高,大,重等）N 倍” 或“A 的长度（宽度,高度,大小,重量等）是 B 的 N 倍”,可用下列几种句型.
1.“A + be + 倍数 + as + 计量形容词原级 + as + B”.
This tree is three times as tall as that one.
这棵树是那棵树的三倍高.
His father is twice as old as he.
他父亲的年纪有他两倍大.
2.“A + be + 倍数 + 计量形容词比较级 + than + B ”
The Yangtze River is almost twice longer than the Pearl River.
长江差不多比珠江长两倍.
The dictionary is exactly five times more expensive than that one.
这本字典比那本恰好贵5倍.
3.“A + be + 倍数 + the + 计量名词 + of + B ”
The newly broadened square id four times the size of the previous one.
新扩建的广场是未扩建时的四倍大.
4.“The + 计量名词 + of + A + be + 倍数 + that + of + B ”
The size of the newly broadened square is four times that of the previous one.
新扩建的广场为以前的四倍大.
5.其它I‘m twice/ double his age.我的年龄是他的两倍.
I‘ve paid five times the usual price for the stamp.
我出了5倍于往常的价格买这枚邮票.
The average income of the staff has been increased by 50 percent compared with last year.
与去年相比,该单位职工的收入增加了50%.
The price of TVs are twofold（ adj.两部分的,双重的） down over these years.
近几年来,电视机的价格下降了两倍.
一、用times表示倍数（一般限于包括基数在内三倍或三倍以上的数.表示两倍的数,一般twice.）.其句型有：
1.times＋形容词（副词）比较级＋than...
This hall is five times bigger than our classroom.这个大厅比我们的教室大五倍.（是我们教室的六倍大）
The car runs twice faster than that truck.这辆轿车的速度比那辆卡车快两倍.（是那辆卡车的三倍快）
2.times＋as＋形容词（或much）或副词原级＋as...
The big box is four times as heavy as the small one.大箱子是小箱子的四倍重.
Asia is four times as large as Europe.亚洲的面积是欧洲的四倍.
Ten is twice as much as five.十是五的两倍.
The plane flew ten times as high as the kite.那架飞机飞行高度是那个风筝的十倍.（高出九倍）
3.times＋the＋名词（size,height,weight,length,width）＋of
Your playground is 900 metres wide,three times the size of ours.你们操场有900米宽,是我们的三倍.
This street is four times the length of that one.这条大街是那条街的四倍长.
This big tree is four times the height of that small one.这棵大树的高度是那棵小树的四倍.（比那棵小树高三倍）
也可译成:The height of the big tree is four times that of that small one.
4.times＋more＋名词（可数,不可数）＋than...
There are four times more books in our library than in yours.我们图书馆藏书（数量）是你们图书馆的四倍.（多三倍）
We have produced twice more grain this year than we did last year.我们今年生产的粮食比去年增长一倍.（是去年的两倍）
5.times ＋as many（或much）＋名词＋其它……
There is three times as much water in this pot as in that one.这个壶里的水（量）是那个壶里的三倍.
There are five times as many students as we expected.到的人是我们预计的五倍.
6.times＋over＋被比对象表示“增加……倍”.如:
The grain output in that village was twice over that of 1978.那个村的粮食产量比一九七八年的增加了两倍.
7.times＋thatof＋被比对象“是……倍”.如:
In this workshop,the output of July was 3.5 times that of January.这个车间七月份的产量是元月份的三点五倍.
二、用...％（percent,per cent）＋up on＋被比对象
Altogether,more than 70 percent of the surface of our planet is covered by water.
我们地球的表面百分之七十以上被水覆盖.
Our factory's output of TV sets in 1998 was 400％ up compared with 1980.1998年我们工厂电视机的产量与1980年相比增长 400％.
The industrial output of last year in our factory was 250％ up on that of 2000.我们工厂去年的工业产量比2000年增加了 250％.（或增加两倍半）
三、用double表示倍数
1.double作形容词,“两倍的”.如:
The production is now double what it was ten years ago.现在的产量是十年前的两倍.
2.double作动词,“是……的两倍”.如:
The output has been doubled in the past five years.过去五年中产量翻了一番.